Boulder, home of the University of Colorado, is ''the New Age's Athens,'' as a local astrologer put it. By some estimates, as many as a quarter of the nearly 80,000 people who live in this town, which spreads beneath the eastern scarp of the Rocky Mountains, have undergone some type of New Age training. Bulletin boards at Boulder's elegant Pearl Street Pedestrian Mall advertise bewildering congeries of ''life and growth empowerment practitioners,'' specialists in ''balancing and aligning energies,'' psychic reprogrammers, past-life regression experts, neuro-linguistic programmers, crystal healers, teachers of ''planetary ascension'' and ''soul merge,'' and ''channelers'' who ''commune with the dead.'' There's even a self-described ''New Age accountant'' who lists ''rebirther'' among his qualifications.

Then there's the Boulder-based Rocky Mountain Spiritual Emergence Network, offering support services for individuals who experience interior voices, a sense of past existence and ''profound estrangement'' from the material world -none of which are viewed by the network as symptoms of psychological disorder; rather, they are regarded as part of a ''natural process of spiritual unfoldment.'' The network's directors include the board president of the Boulder County Health Department and the nurse manager of Boulder Community Hospital's medical-psychiatric unit. So rapidly do fashions of the spirit proliferate in Boulder that, by comparison to some of the newer arrivals, the 14-year-old Naropa Institute, ''a contemplative college'' founded by the late Tibetan Buddhist Chogyam Trungpa Rinpoche, seems as staid as the Episcopal Church.

The current efflorescence of New Age spiritualism in Colorado trades partly on the state's traditional tolerance for unorthodox religion. In 1946, a columnist for The Rocky Mountain News declared, ''I am proud rather than regretful that Denver is a city of cults. The fact that we seek new ways - sometimes wrong ways indeed -toward the eternal verities is evidence we are a lively and aspiring community.''

Since the 1960's, the state has welcomed a steady stream of spiritual immigrants. A few of the more prominent: Jose Arguelles, a mystic who conceived last year's mass meditation known as the ''harmonic convergence''; the popular astrologer Linda Goodman; Shirley MacLaine, who wants to establish a center for ''healing'' and metaphysical study in the town of Crestone, and the entertainer John Denver, whose Aspen-based Windstar Foundation has brought together New Age theorists and various public figures, including Ted Turner, J. Peter Grace and former Colorado Gov. Richard D. Lamm. ''You see the footprints of New Age attitudes and assumptions all over this state,'' says John K. Andrews, president of the Independence Institute, a nonpartisan public policy research group based in Denver. ''Because of the large number of in-migrants, the high educational level and the traditional openness to new approaches, people here may be more vulnerable than elsewhere to the New Age appeal.''

The mainstreaming of the transcendental began in earnest when countercultural migrants, who had been attracted to Colorado in the 1960's by its cheap land, relative isolation and mountain mystique, fused with the massive influx of young professionals drawn by the state's economic boom in the 1970's. Between 1960 and 1987, Colorado's population leaped to 3.3 million from 1.75 million, as the state shifted from a horse-and-buggy economy based on mining and ranching to one fueled by new high-technology corporations, government offices and financial services tied to the for-a-time-booming oil industry.

When oil prices collapsed in the early 1980's, the economy plummeted along with them, and the growing popularity of New Age ideas may to some extent reflect short-term economic and social demoralization. The boom's end left Denver with a spanking new core of skyscrapers that stand as half-empty monuments to a surge of prosperity Coloradans thought would never end. It also left the state with unemployment of almost 8 percent in 1987.

''For a long time, we had a competitive, sort of John Wayne attitude toward business,'' says a Denver businessman who is active in New Age groups. ''What we now need is cooperation, room for the magnificence of each of us to create an atmosphere where everyone can win, where there are no losers.'' The fact that New Age idealism seems to appeal as much to the successful as to the unsuccessful suggests, however, that there are deeper reasons for its popularity.