In a program at the attractively remodeled Publick Playhouse Friday night, the Maryland Dance Theater celebrated its 15th anniversary by reconfirming the virtues that have made it one of the area's pacesetting institutions.

The troupe, founded in 1971, is in residence at the University of Maryland, from which base it tours the state and other parts of the eastern seaboard. There's a built-in turnover factor in the company mix of faculty, students and professional free-lancers, as illustrated by the proportions of this year's ensemble -- fully half the dancers are new. Nevertheless, throughout most of the evening, the dancing displayed the spirit, discipline and artistic savvy that have become MDT trademarks. The occasion also saw the troupe reasserting its image as defender of the faith in its fidelity to the traditional stylistic core of modern dance.

At the same time, it was dismaying to find the choreography so lopsidedly tilted toward bland conservatism, an MDT tendency of the past here intensified. As far as this program was concerned, it was as if the last quarter-century of innovation -- from Cunningham and the Judson era to today's frontier -- never happened. For a company so dedicated to an educational mission, one would hope to see a repertory more reflective of vital contemporary trends.

A revival of Murray Louis' 1956 "Bach Suite" led off the evening on the wrong foot. The piece -- twitchy, flighty and overfilled with steps -- is far from Louis' best, and an edgy, deliberate performance made it look all the more trifling.

The program's closest approach to novelty was Becci Parsons' "Tsunami," which won an award at this year's American College Dance Festival. It's a ritualistic paean to water, originally created in a video version for a symposium on oceanography. The dancers, in vaguely eastern garb, enter holding bowls of water aloft. They lean, arch and sway to a mostly unintelligible recorded text. In a second section, accompanied by whispers, they hover over the bowls, make the rims sing by rubbing them and gently douse themselves. After a more animated passage, they reform their starting diagonal and spill the liquid from the raised bowls onto their worshiping figures.

The choreography is not without atmospheric and compositional flair, but its exoticism seems synthetic and its tone precious -- the work of a promising fledgling, perhaps, but an odd choice for one of MDT's limited repertory slots. Also disappointing, though persuasively performed, was Anne Warren's new "Dance for Strings," a neatly crafted but monochromatic exercise in lyrical fall-and-recovery set to humdrum 18th-century chamber music.

The revival of MDT director Larry Warren's "Post Cards" (1981) had the salt and pepper the other offerings lacked. As the work's five couples gravitate through a morning picnic and surfside frolic toward a dusk of amatory consummation, the shrewdly observant choreography develops a piquant picture of summer libido at high tide.

Also on the positive side here and throughout the program was Paul Jackson's dramatically apt lighting.