It is not as random as Rockville, and not as rural as Olney. It is nowhere near as old and stately as Chevy Chase, but it is far less congested than Bethesda.

It lacks the wealth of Potomac and the ethnic diversity of Silver Spring. But it offers cows, clean air, lots of space, freeway access and home prices under $50,000 - and almost no other place in Montgomery County can say all that.

The area is the corridor along Interstate 270 - a strip about nine miles wide and 25 miles long, running northwest from Rockville to the Frederick County border.

Just 15 years ago, the I-270 corridor was farms, woods and nothingness. Today, two-mile backups at freeway ramps are common during rush hour.

Just 14 years ago, Kettler Brothers revealed to the Gaithersburg town council its plan to build the now-sprawling Montgomery Village complex beside I-270. "We said, 'You city boys and gonna do What?' " recalls William N. Hurley Jr., then a council member and now a Kettler Brothers vice president. "But we've done it. And you can see all the rest who have."

Just 13 years ago, Montgomery County issued its "wedges and corridors" master development plan. It called for intensive development along major roadways, with "wedges" left either undeveloped or less thickly developed between. It was the first time a master plan had been developed for the I-270 corridor.

Then, seven years ago, the first in a series of sewer moratoria was instituted in Montgomery County. Since then, the effect has been to drive the prices of existing homes through the ionosphere, and to all but halt new construction everywhere but in the corridor.

There, more than 10,000 sewer connections had been authorized during the 1950s, decades before anyone had begun, or even seriously contemplated, the kind of development now in progress. Homes now being built in Germantown and Gaithersburg are using those "early" authorizations.

And the homes are being built at a terrific rate. To drive along the interstate is to see bulldozers, trucks full of building supplies, half-finished homes and homes that have obviously weathered only a few winters.

Nowhere is the burgeoning as broad as in Germantown. And despite the uncertainty over sewers, it promises to continue. According to Montgomery County plans to projections, the I-270 corridor, and particularly the Germantown sector, will be the site of the next great Washington area real estate boom between now and 1986.

In the next nine years, according to a county government projection, population in the I-270 corridor is expected to swell from 63,000 to about 109,000. It may go as high as 123,000.

In the same period, the number of dwelling units in the corridor is expected to grow from about 21,000 to 37,404 will 1986. Of those, about three-fourths will be single-family homes, the county predicts.

In 1978, Taubman and Co., a Michigan real estate developer, is expected to open the Lake Forest shopping center beside the intersection of state Rte. 335 and Montogomery Village Avenue. The centre will be the largest in the county, half again as large as Montgomery Mall. It will feature five major department stores, including a Woodward and Lothrop and a Sears Roebuck.

By 1982, Metrorail is scheduled to extend as far as Gaithersburg. And by the same year, according to present plans, none of them yet funded, two new major north-south highways and two new I-270 interchanges will have been added in Germantown, and Rte. 355 will have been widened to six lanes to well north of Gaithersburg.

Yet the result of all this development - how the northern county will look, how it will "feel," who will live there - is still uncertain.

The chief problem appears to be timing, or as the planners call it, staging. Will housing be in place before roads are improved? Will schools be there as soon as the population is? Is there a way to assure that neither politics nor profit motives overwhelm order and unspoiled landscape?

"There's always going to be a lag, unfortunately," admitted John Otto Mathias, the county planner responsible since 1972 for development in Germantown. "It could overrun itself, yes. Even if we wanted to stay rural, that's not public policy, unfortunately."

"It has its problems," acknowledged Frederick Agostino, assistant director of the county government's office of economic and agricultural development. "We'd like more diversification (along I-270). It makes you a better-rounded community."

"The whole thing is the cart before the horse," insisted Aubrey Bladen, 53, a lifelong county resident and frequent foe of the I-270 planning forces. "There's a false sense of security because of I-270 itself . . . I am opposed to making the county landscape a patchwork of highways."

"I don't think you could do something like Montgomery Village again, not on the same scale," said Hurley of Kettler Brothers. "We were fortunate in terms of timing. The price of land and the uncertainties of the market now are just too much."

But despite the doubts and questions, people are trooping into the corridor to live. Who they are and where they are coming from is a hint of what, and who, lies ahead.

Pat and Joan Michielli, for example, bought a two-bedroom town house in the Cinnamon Woods subdivision of Germantown three years ago. They paid $34,500. They had to put only five per cent down.

It was and is their first home. They are both 30, and are expecting their first child this summer.

Pat Michielli, who grew up in Prince George's County, is a systems analyst for a Germantown computer company that does contract work for the Energy Research and Development Administration. John Michielli, who grew up in the countryside near Dublin, Ireland, is a secretary at the Bethesda headquarters of the Marriott Corporation.

The Michiellis have been married for five years. For the first two, they lived in an apartment in Hyattsville. They bought their home in Germantown even before Pat Michielli's office moved from Silver Spring to right nearby. Michielli said the couple was willing to endure a 45-minute commute "just so we could be in the countryside."

Their home sits about 15 strides from a community swimming pool. On a nearby hill, belonging to a farmer, animals graze. Just across the nearest main street, Clopper Road, lies Seneca Creek State Park. "For me to pack up from here and go to Silver Spring or Wheaton, no way," said Pat Michielli. "Even if I had $80,000, which I don't, I still wouldn't."

Most of the neighbors in the Michiellis' cul-de-sac are couples about the same age, but the Michiellis said they don't miss having older people around. And although goods or services require a drive of at least four miles, the Michiellis said they don't mind.

Obviously, though, they are dependent on a car, or in their case, two. And dependence on cars is a central fact of life along 1-270.

The strange part is the dependence appears to be a matter of choice, despite the inevitable congestion. Even though bus service and Baltimore and Ohio commuter train service are available from both Germatown and Gaithersburg, few use either.

Hurley said that Montgomery Village, now home to 16,000 souls, many of whom work in the District, experimented last year with express buses direct to the Federal Triangle. Running time was about the same as by car, parking was unnecessary, schedules were convenient and the driving was left to someone else.

"We averaged three people a day," Hurley said. The service has recently been abandoned.

Regularly scheduled Metrobuses, regardless of destination, have fared little better, according to officials. And car pooling, while somewhat more common along 1-270 than elsewhere in the county, is still statisically insignificant.

The arrival of the subway at Shady Grove Road is expected to ease matters somewhat. County planners are trying to maximize its use by proposing a "link road" - tentatively named 1-370 - that would provide high-speed access to a parking lot of 3,000 spaces right beside the station.

Another major help is expected to be the two new main roads and two new 1-270 interchanges in German-town.

The new roads, named the eastern and western arterials, would be four lane divided highways flanking 1-270 and running from Gaithersburg to well north of Germantown. The idea is to give local traffic in alternative to 270.

New 1-270 interchanges would be constructed at Middlebrook Road in Germantown and at Waters Road just north of Germantown. The present Germantown interchange at state Rte. 118, the town's one and only, would be closed.

In addition, according to Matthias, plans are "in the preparation stage" for a new 1-270 interchange at Falls Road in Rockville. Downtown Rockville now has only one interchange, at West Montgomery Avenue (Rte.28). Traffic exciting there in evening rush hour often produces a blockage, making for an even longer commute for those who live farther north along 270.

Sewer capacity may be more pressing problem in the development of the 1-270 corridor, however.

Future capacity must come from a new facility, and it will be built only if the county, the state and the Environmental Protection Agency can agree on location and funding. So far, they have not.

As a result, several builders have taken matters into their own hands. Kettler Brothers recently finished its own Montgomery Village treatment facility, at a cost of "a couple of million dollars," Hurley said. At least two of the six developers now building in Germantown have done or are doing the same.

Meanwhile, the county has freed up sewage capacity in other ways.

Last year, the county finished its Seneca Interim Treatment Plant, which has a capacity of six million gallons a day. About 70 per cent of the capacity was allocated to private homes and apartments.

When the county went to a landfill system for its solid waste last year, rather than open air fires later doused with water, it picked up a windfall of 800,000 gallons of capacity a day. About three-eights of that goes to private residences.

"As of today, we are better off, sewerwise, than in the last five years," said Agostino.

The one part of the 1-270 corridor that has escaped the immediate development crunch is the northern fourth - from Clarksburg to the Frederick County line. The reason is that county sewer lines do not extend past Germantown. According to a county master plan for Clarksburg, the area will remain in its present state of farms and rolling hills for the foreseeable future.

But Germantown and Gaithesburg won't.

"It'll be worse than Silver Spring some day," warns Aubrey Bladen. "I'm not really worried," replies Pat Michielli. "No one's going to be here forever. Within Montgomery County, this is the nicest."