Tired of the hassle of city life, of hard commutes, of school and crime and pollution problems? Thinking of a move from metropolitan America to some small town or country area?

If so, you're in ample company. Through virtually all of U.S. history, the population trend was constant: People left the farms and small towns and migrated to jobs and opportunities in the cities. But around 1970, a remarkable shift occurred as more people -- about 300,000 to 400,000 a year, in net figures -- began the reverse, back-to-the-land shift out of the metropolitan areas.

Why this dramatic change? Who are the exurbanites, and where are they headed in rural America? Will their departure harm the big cities and suburbs? Will the rural areas become so glutted with new residents that they will lose the very quiet charms and elbow room that make them so attractive? Will gasoline shortages slow the trend?

Unanimous in failing to predict the new trend, the demographers now have a long list of explanations.

Polls show that Americans generally prefer country living, and by 1970 many more could carry out that dream. Superhighways made long commutes to cities or suburban work sites feasible. People were retiring earlier and receiving generous pensions, permitting a fresh start in a new place.

With affluence, more people sought out homes near summer or winter recreation spots. Manufacturing, in search of cheap land and lower-paid labor, was dispersing to the country-side. Recreation and service industries created more and more rural jobs.

And such age-old scourges of rural life as mud roads and pellagra, isolation, brackish wells and grinding poverty had, for most people, all but disappeared. In their place came all-weather roads, electricity, telephones, adequate health services and constant contact with the outside world through decent radio and television reception.

In times past, the rural areas "exported" their poor and ill-educated to the cities. What they're now receiving in return is quite different -- affluent part-time commuters, young professionals, retired executives, mining engineers, resort managers, craftsmen and artists, unemployed idealists and returning natives -- even southern blacks -- who've decided they prefer life at home to the city.

Where in rural America are all the people going? Some are actually far-out suburbanites, settling in the distant rural orbit of such cities as Washington, St. Louis, Nashville, Atlanta and Minneapolis. But surprisingly, the rural counties with the least commuting, the most distant from metropolitan areas, are now getting a major share of the new migrants.

There are the sun-seekers in rural Florida and the Southwest. But waves of retirees have headed for country parts of Missouri, Arkansas, Oregon and even chilly upper Michigan and northern New England. Outlying factories draw people to the rural South, Idaho, Wisconsin and parts of Appalachia.

So-called alternative lifestyles draw immigrants to rural New Mexico, Colorado and New England. And there are the now-expanding energy boomtowns of the western mountains, Kentucky and West Virginia.

It's true that hundreds of rural counties -- especially in the Great Plains and the old Dixie Cotton Belt -- are still losing people. But they are the exceptions. In history, the 1970s will be remembered as the decade of rural return.

Will all this harm the big cities and their suburbs? Probably not. The country's 281 metropolitan areas have an overwhelming 73 percent of the people.

The most serious victim of the rural return could be rural America itself. We're not seeing a return to the land as much as a dispersal of urban America into the countryside. Joseph Doherty, in a report for the Urban Land Institute, calls it the countryfied city -- an extension of small-city conditions and activities on a county or multi-county scale.

His example is Montgomery County, N.C., where most people live outside the towns and but choose a suburban style. They live in split-levels and bungalows on a few acres, in tiny subdivisions or in mobile homes; they work in office, factories or service jobs; they send their children to suburban-like consolidated schools; they shop mainly in suburban-type shopping centers.

Most rural communities are ill-equipped to deal with sudden population growth. Many are repeating the wasteful, spawling patterns of metropolitan suburbs. North Carolina, for instance, found the new population was concentrating adjacent to, but outside, the boundaries of small incorporated cities. New subdivisions, shopping centers and plants escape the tax reach of those small cities, creating a rural mirror of the "hole in the doughnut" problem typical of troubled metropolises.

All of this is horrendously expensive, says North Carolina state official Arnold Zogry: "There's no way you'll have funds available to develop all these into thriving centers" with water and sewer lines, police, fire and other services.

Doherty depicts the growth of linear suburbs -- houses and mobile homes, soon joined by fast-food pit stops, convenience stores, small subdivisions and shopping centers -- stretching between towns and sapping the strength of the rural towns and small cities.Without good zoning and planning, the country-side soon becomes despoiled. Yet the thought of controls, Doherty says, often "prompts the countryman to reach for his rifle."

Even with a will, rural local governments are ill-equipped to deal with the onslaught. Counting counties, townships, villages, special districts and Indian reservations, there are tens of thousands of units trying to serve an increasingly diverse and demanding population of exurbanites who have often chosen an unincorporated place to live.

The great governor of rural growth may be energy shortages: County areas are overwhelmingly dependent on the internal combustion engine. A moderate pinch in gas supplies might be the best news for these areas. It would permit them to grow a bit more slowly, to plan better, and perhaps to preserve the vistas, the uncrowded atmosphere, the very rural quality of life that makes them so desirable in the first instance.