If you've ever taken a guided bus tour, you probably were annoyed at least once by the couple who kept everybody waiting while they made one more purchase at the inevitable gift shop on the itinerary.

Why do they tarry, you think, when there is so much to see?

To many travelers abroad, however, shopping is as important a part of the trip as sampling exotic foods and visiting great art treasures. Some have filled their homes with mementos of their trips. And even confirmed nonshoppers usually return with a trinket or two for family and friends.

The strength of the dollar (despite some weakening in recent weeks) has added incentive to the shopping urge. The bargains available abroad in clothing, leather goods, crystal, china, perfumes and fashion items are often too tempting to ignore.

Such obvious interest in shopping has led tour organizers to offer a variety of shopping tour packages to Europe and the Orient. You travel with a group of like-minded consumers, whose main reason for traveling is to buy, and so everybody tarries in the stores.

Shopping tours are particularly popular with frequent travelers, says Randy Tom of Amity Tours in Redwood City, Calif., which arranges shopping excursions to the Orient. Many of his clients already have seen the major sites and are returning to browse the stores they didn't have time for on an earlier visit.

Many women leave their husbands at home, he says, and travel with another woman (or a group of women) who enjoys shopping.

On some tours, a guide accompanies participants to selected shops and department stores; on others, participants are sent off to shop on their own, carrying a list of recommended places to try. Most tours include some sightseeing.

Several organized buying sprees have been scheduled for this fall so that travelers, as the brochures suggest, can do their Christmas shopping at leisure while having their evenings free to enjoy the fine dining and nightlife of the world's great capitals.

Air fares and hotel prices generally are cheaper in the fall, and many shops put merchandise on sale once the summer tourist season is over.

Among the scheduled tours:

Amity Tours' Orient "Shopper's Paradise": One of the more elaborate shopping tours, the "Shopper's Paradise" is a 15-day look at the marketplaces of Hong Kong, Bangkok and Singapore.

Included is a half-day's visit to some of Hong Kong's fashion warehouses, where those "Made in Hong Kong" labels are added to cashmere sweaters, silk blouses and other designer items before they are shipped to department stores and boutiques in the United States.

Escorted tours are also planned to gem factories and modern shopping complexes as well as "side-street specialty shops."

Good buys, says trip organizer Randy Tom, are jewelry, furs, antiques, oriental handicrafts and rugs and tailored clothing, including made-to-order suits in Hong Kong for women and suits and shirts for large, hard-to-fit men. The tour remains five days in Hong Kong so fittings can be scheduled.

Tom limits the tours to no more than 25 participants. Part of each stay includes local sightseeing (a sunset cruise in Hong Kong harbor; a tour of the magnificent Grand Palace in Bangkok); and evenings are devoted to group dinners so shoppers can share their day's experiences.

The tour concludes with two nights at a beach hotel in Hawaii -- and more shopping for those who have any money left.

The price is $1,999 per person (double occupancy), which includes round-trip air fare on Singapore Airlines from San Francisco; accommodations in deluxe and first-class hotels; hotel/airport transfers; selected meals; and sightseeing. Departures Nov. 7, Nov. 9 and Feb. 22.

For information: Amity Tours, 2710 El Camino Real, Redwood City, Calif. 94036, (415) 364-5930 or (800) 523-8406.

Passages Unlimited's "London Pre-Holiday Shopping Spree": In this seven-night package, shoppers are given an "Insiders" guide to the best buys in London, and there is a host on hand at their hotel to provide up-to-the-minute tips on department store sales.

Accommodations are in an apartment hotel (studio apartments) near Oxford Street, one of London's principal shopping areas. The host can also help arrange for sightseeing, dinner reservations and theater and concert tickets.

The price is $699 per person (double occupancy), which includes round-trip air fare from New York City on Pan Am; accommodations; hotel/airport transfers; and a "welcome food basket." Departures every Tuesday from October through mid-December.

The company offers a three-night add-on in Paris for an additional $300 per person, including London-to-Paris air fare and lodging in an apartment hotel.

For information: Passages Unlimited Inc., 48 Union St., Stamford, Conn. 06906, (800) 472-7724.

* GWV Travel's London "Shopping Spree": GWV Travel promises shoppers' discounts on such famous British merchandise as rainwear, sweaters, crystal and porcelain on its six-night package to London.

On the otherwise open agenda is a half-day sightseeing tour of such city attractions as Westminster Abbey and St. Paul's Cathedral. The rest of the time is available for shopping, as you wish.

The package begins at $579 per person (double occupancy), including round-trip air fare from New York City on a charter airline; six nights lodging in a superior tourist hotel; hotel/airport transfers; and sightseeing. Departures every Friday through September and every Saturday from Oct. 5 to Oct. 26.

For information: See a travel agent; or contact GWV Travel, 140 Gould St., Needham Heights, Mass. 02194, (617) 449-5460.

* Icelandair's "Bargain Sprees" to Iceland and Europe: Icelandair offers a series of shopping packages, including a weekend in Iceland; a six-day tour that includes Iceland and Scotland; and five- or six-night stays in Paris, Zurich or Luxembourg.

One of its most popular packages, inaugurated last fall, is the Iceland weekend, which combines a half-day's visit to the country's woolen factories and outlets and a full day's tour of the remarkable countryside, with its geysers, mountains and waterfalls. Fashion shows are scheduled in the evening.

The itinerary is full, but there's plenty of time for shopping. Departures are every Thursday evening (Nov. 7 through March 13) from Baltimore/Washington International, with arrival at the hotel in Reykjavik about 8 a.m. Friday. Participants can nap until 12:30, and then it's time for lunch and an afternoon at the woolen outlets.

Saturday is devoted entirely to countryside sightseeing, and the weekend concludes Sunday with a "Viking brunch." The price is $349 per person (double occupancy), including air fare; two nights lodging; hotel/airport transfers; sightseeing; and selected meals.

A six-day shopping and sightseeing trip to Iceland and the cities of Edinburgh and Perth in Scotland departs New York City on Sept. 2, 9, 16 and 23. The itinerary includes woolen outlets in Iceland and a crystal factory and distillery in Scotland. The price is $669 per person (double occupancy), and includes air fare, lodging, breakfasts, two Scottish dinners and sightseeing.

Iceland's tours to Paris, Zurich or Luxembourg range from $499 to $629 per person (double occupancy), depending on the departure date. The price includes round-trip air fare; lodging; continental breakfasts; hotel/airport transfers; and sightseeing.

There are weekly flights from Baltimore/Washington from September into December.

The Paris and Zurich packages are basically do-it-yourself shopping tours, but the Luxembourg package offers an escorted shopping excursion to a porcelainware plant, a semiprecious stone-cutting center and the ancient city of Trier in West Germany.

For information: See a travel agent or contact Icelandair, (800) 223-5500).

Here are some tips if you decide to go shopping:

* Find out what prices are at home for items that interest you, so you will know if you are getting a bargain abroad.

* Read up on gems and furs, or other expensive items you expect to buy, so you know the difference between quality and inferior merchandise.

* Be familiar with U.S. Customs regulations, so you know how much duty, if any, you will have to pay on your purchases. Most tour organizers provide this information.

* Take along an empty suitcase (or plan to buy one abroad) for your purchases. Travel light so you won't have to pay excess baggage charges.

* Complete the necessary steps to obtain a refund of value-added taxes, a form of sales tax in Europe that can be as much as 22 percent. You are entitled to the refund in most countries for items you are shipping or carrying home, but you have to apply for it.

* "Negotiate" in the Orient, says Amity's Randy Tom. "If you don't, the merchants don't respect you."

NEW FLIGHTS: They are a year away, but Pan Am is promising daily nonstop flights from Washington/Dulles to Madrid next summer.

Currently, travelers to Spain must connect in New York City for a Madrid flight. Pan Am now flies from Washington/Dulles nonstop to London and Frankfurt.

And beginning Dec. 23, a major charter operator, Wainwright Travel of Bethlehem, Pa., will be offering weekly five-night charter packages from Baltimore/Washington to the Caribbean island of Curacao.

The price will range from $399 to $509 per person (double occupancy), depending on the quality of hotel chosen. Included are air fare, lodging and hotel/airport transfers. For more information on the "Curacao Fling": Curacao Tourist Board, 400 Madison Ave., Suite 311, New York, N.Y. 10017, (212) 751-8266.