Chris Skow, a Union Pacific freight conductor, is one of those nostalgia buffs who go bonkers over trains. He loves them all, but especially the aged trains that ply the high mountains of Latin America. The romance of rail travel still flourishes south of the border, he says, and allows you to step back into the 1940s. In the past two decades, he's made 55 trips to satisfy his offbeat passion.

But there's a practical side to Skow too. Five years ago, he began taking groups of about 40 paying tourists with him on his rail journeys south. On each of these special trips, he charters private rail cars -- sometimes pulled by an old-fashioned, steam-powered engine -- and plans an itinerary through some of the region's most scenic countryside. His firm, Trains Unlimited, Tours, is based in Reno, Nev.

Skow is one of numerous tour operators who have found a growing market in escorted tours by rail in this country and abroad. The trips attract travelers who, like Skow, find train travel fascinating and -- yes -- romantic. Rail fans can sign up for tours -- "rail cruises" they are sometimes called -- of the American Southwest, Southern Europe, the Alps, East Africa, the Malay Peninsula, the Soviet Union, China, Guatemala and South America.

"There seems to be a resurgence of interest in train travel," says Chris Kaemmerer, vice president of Circle America Tours, a St. Louis company offering a variety of rail trips in this country.

A tour by rail can take many forms, and travelers should determine in advance the nature of the tour they are purchasing.

On some of Skow's tours, passengers travel on private rail cars attached to inter-city trains or chartered trains. In contrast, Circle America Tours books its groups on Amtrak rail cars. Most of Circle America's U.S. trips depart from a station reached by Amtrak, so participants who don't like to fly can travel from home by train. It also links Caribbean and Alaskan cruises with rail travel from home.

Adventurous travelers who opt for the Asian Express will travel the length of the Malay Peninsula by rail from Singapore to Kuala Lumpur and Penang in Malaysia and Bangkok and Chiang Mai in Thailand. The 15-day escorted tour is offered by Globetrotters World, a New Zealand organization. But continuous rail travel is often the exception rather than the rule on rail tours. Amtrak itself puts together several U.S. tour packages that combine rail travel with motor-coach touring to scenic and historic sites not served by train.

Europe Train Tours, a Swiss company specializing in rail tours of the Alps, combines inter-city travel over famous mountain routes with a number of sightseeing day trips by rail from Swiss cities. In a variation, Skow links some of the best sightseeing rail trips in the West -- including the historic Durango & Silverton Narrow Gauge Railroad in Colorado -- in a 15-day rail and motor-coach tour he calls the Rocky Mountain Spectacular.

On some trips, you may sleep aboard the train occasionally. For example, on the Trans-Siberian Railroad Adventure, an 18-day tour that includes rail travel from Moscow to Irkutsk in Siberia, passengers spend three nights aboard in first-class cars. The escorted Siberian tour is offered monthly by the Russian Travel Bureau, a U.S. tour company in New York. However, most escorted rail tours feature rail travel by day only with nights spent in hotels, motels or inns.

Escorted train tours tend to attract older travelers, although the more adventurous trips, such as Skow's Latin American itineraries, appeal to a wider age range because they are difficult to duplicate independently.

If train touring appeals to you, check with the tourism office of a state or country that you plan to visit for information about unusual train rides. A number of historic trains are operated for tourists throughout the United States. And the national rail lines in Europe often highlight especially scenic routes. Many tour operators and rail lines, including Amtrak, also have put together lodging and rail packages for independent travelers.

Among the firms offering escorted rail tours:

Trains Unlimited. Currently, Skow's firm features five basic itineraries -- Guatemala, Ecuador, southern South America (Chile, Argentina, Paraguay), the Rocky Mountain West and California. In addition, Skow is the U.S. representative for a British company, Railway Travel and Photography, that operates rail tours in China, East Africa, rural France, Spain and Northern Europe.

Both Skow and the British firm generally combine travel by rail and bus with overnight lodging off the train.

Skow's Great Guatemalan Train Adventure is a nine-day odyssey that crosses the mountainous Central American country from its Pacific coast to the Caribbean. The route passes through remote countryside reached only by rail, says Skow. Travel is in private cars attached to four separate chartered trains. A chartered motor coach follows by road to provide transportation between the trains and lodgings. Departure is Jan. 26 in 1991 and Feb. 21 in 1992. The cost for 1991 is $1,695 per person (double), which includes air fare from Miami, lodging and most meals.

The Ecuadorian Eclipse Express, a nine-day excursion departing July 4, makes use of chartered steam trains to explore the Ecuadorian Andes, including colonial cities and volcanoes. At Ecuador's famous Devil's Nose Switchback, the train descends a steep rocky face in a series of zigzag maneuvers. Passengers can view a partial eclipse of the sun in Ecuador. The cost is $1,949 per person from Miami with add-on options for four days in an Amazon River lodge or a yacht cruise of the Galapagos Islands.

The Deep South Latin Express is a 30-day trip mostly by train through Chile, Argentina and Paraguay. Shorter options are available, and you can extend the tour with a trip to Tierra del Fuego at the southern tip of the continent. The basic itinerary features nine train rides -- including the Old Patagonian Express -- in a loop that begins and ends in Santiago, Chile. The tour visits Iguacu Falls on the Argentine-Paraguayan border, the Argentine mountain resort of Bariloche and several national parks. The cost for the 30-day trip is $5,795 per person from Miami.

The Rocky Mountain Spectacular is a 14-day trip that departs Oakland, Calif., on Oct. 5. On the initial leg, the firm's two private rail cars and a sleeper car are attached to Amtrak's California Zephyr for the two-day ride across the Sierras and the Rockies to Denver. In Denver, passengers board a motor coach for several days of mountain sightseeing, including day trips on a variety of scenic rail lines. In Flagstaff, Ariz., participants catch Amtrak's Southwest Chief for Los Angeles. The cost is $2,519 per person, which includes transportation from Oakland, lodging and 30 meals.

Golden State Rails is a 12-day tour of California from the northern Sierras south to San Diego. Much of the travel is by bus, but 12 separate train rides are scheduled. After touring palatial Hearst Castle, participants board the firm's two private rail cars in San Luis Obispo. The cars will be attached to Amtrak's Coast Starlight bound for Los Angeles. The tour departs July 3, and the cost from Oakland is $1,498 per person.

Information: Trains Unlimited, Tours, 235 W. Pueblo, Reno, Nev. 89509, 800-359-4870 and 702-329-5590.

Globetrotters World, a New Zealand firm, has organized two unusual escorted tours featuring long-distance travel by trains, the Asian Express and the London Express.

The Asian Express is a 15-day tour that provides travelers with a close-up look at Asia beyond its major cities. Participants travel by train from Singapore to Bangkok and northern Thailand with stops en route at Kuala Lumpur, the Malaysian capital and the island resort of Penang. The tour departs every Saturday, but there must be a minimum of 15 passengers for an escort. The cost begins at $1,690 per person (double), which includes 12 nights lodging and two nights in a sleeper car. Air fare is additional.

The London Express is a 17-day trip from Beijing to London via Ulan Bator in Mongolia, the Trans-Siberian Railroad from Irkutsk, Moscow, Leningrad, Warsaw and Berlin. Several nights are spent aboard sleeping cars. Departures from Beijing are May 1, May 29, July 31 and Sept. 4. The cost begins at $2,800 per person, which includes lodging and most meals until Warsaw.

Information: Contact the New Zealand Central Reservations Office, an organization representing New Zealand tour firms, in Los Angeles at 800-351-2323.

Circle America Tours. All but a few of Circle America's thick catalogue of U.S. tours begin in a city reached by Amtrak. Many of the tours link a leg of rail travel with bus sightseeing, but at least two include a substantial ride on Amtrak, the Southern Springtime Swing and Windows of the Great Southwest. Lodging is off the train.

The eight-day Southern Swing originates in New Orleans, heads east to Atlanta and then doubles back via Birmingham and Montgomery to Mobile, Ala. Except for a bus leg from Mobile back to New Orleans, travel is by Amtrak. There are weekly departures in March, April and May. The cost is $1,265 per person (double) if you fly to New Orleans from Washington and $1,069 if you take the train. Included is lodging and nine meals.

The eight-day Windows of the Great Southwest begins in Phoenix and then continues via Amtrak to El Paso, Tex. In Alpine in southwestern Texas, participants board a bus for Big Bend National Park, where a half-day scenic float trip on the Rio Grande is scheduled. The tour returns to Phoenix on Amtrak with an overnight stop in Tucson. There are frequent departures from Feb. 2 to Nov. 2. The cost is $1,395 per person, which includes air fare from Washington, lodging and 10 meals.

Information: Circle America Tours, 7531 Ravensridge Rd., St. Louis, Mo. 63119, 314-968-9009.

Europe Train Tours, a Swiss firm, has put together a variety of escorted train excursions in the Swiss Alps. Nights are spent off the train.

One of the most popular is the 12-day Glacier Express Spectacular, which includes a ride on the country's famed Glacier Express from St. Moritz to the town of Zermatt at the foot of the Matterhorn. Lucerne, Interlaken, Montreaux and several scenic train rides are also on the itinerary. Departures are frequent from May 16 into October. The price from Zurich is $1,991 per person (double), which includes lodging and most meals.

Information: Europe Train Tours, 198 E. Boston Post Rd., Mamaroneck, N.Y. 10543, 800-551-2085 and 914-698-9426.

Russian Travel Bureau. For 20 years, this U.S. firm has been escorting Americans on its 18-day Trans-Siberian Railroad Adventure. Departures are monthly except in May and June when two trips are scheduled.

The tour takes in Leningrad, Tashkent and Samarkand as well as the Trans-Siberian rail journey from Moscow to Irkutsk in Siberia. Three nights are spent on the train. The cost begins at $2,999, which includes air fare from New York, lodging and meals.

Information: Russian Travel Bureau, 225 East 44th St., New York, N.Y. 10017, 800-847-1800 and 212-986-1500.

Amtrak offers a variety of independent and escorted tour packages. They have been so successful, says Amtrak spokeswoman Pat Kelly, that Amtrak is reorganizing the tour program to make it easier for passengers and travel agents to book vacation packages.

As part of the new plan that takes effect Jan. 1, Amtrak's tours will be handled by a tour wholesaler, MTI Vacations of Chicago. Amtrak is expected to announce tomorrow a new Air-Rail Travel Plan link-up with United Airlines that will enable passengers to make round trips using Amtrak one way and United the other at package prices. Information: 800-USA-RAIL (800-872-7245).

Offbeat India A small Arlington tour firm, Cross Cultural Adventures, has received permission to lead a 14-person cultural tour into Bastar, one of the most undeveloped and restricted regions of India. Bastar is home to some 62 aboriginal tribes who reportedly live without machinery or other modern devices much as their ancestors did.

Located in eastern India about midway between Calcutta and Madras, Bastar is an area of rugged hills and lush forests. India has been eager to preserve the primitive culture there and restricts access by outsiders. Cross Cultural Adventures became the first Western firm permitted to enter following a successful tour this year to Nagaland, another restricted area.

In tribal villages, participants will observe the weekly outdoor bazaars, where opulent ornamental beadwork is bartered. The trip begins in the temple city of Bhubaneshwar, site of the Sun Temple of Konarak, noted for its erotic images. One night is spent in the palace of the Maharaja of Kawardha and the trip concludes in Kanha National Park, a tiger preserve.

The tour departs Feb. 1. The cost is $2,800 per person, which includes accommodations and meals. Air fare to India is additional. Lodging in cities is deluxe, and the forest lodge at Kanha is described as good. In Bastar, participants will be lodged in tourist bungalows or at campsites.

Information: Cross Cultural Adventures, P.O. Box 3285, Arlington, Va. 22203, 703-204-2717.

Hana Update

In a story about my drive on Maui's Hana Highway in last Sunday's Travel section, I mentioned visiting the Hasegawa General Store in Hana. Unfortunately, the popular tourist stop was destroyed by fire recently, as a reader pointed out. But the store will be rebuilt, according to owner Harry Hasegawa, and in an architectural style more fitting to its long history on the island.

The building that was lost was built in 1957, says Hasegawa, whose family has run a Hana store since 1910. Plans are being drawn up for a new building that will reflect the Victorian era when the store was founded. He expects it to be completed in 1993, if not earlier. Meanwhile, he is renovating the old Hana Theater as temporary quarters for the store and hopes to open next month.