In celebration of National Dance Week, Dancefest '85 filled Glen Echo Park this weekend with two days and nights of wall-to-wall dance events ranging from panel discussions on teaching and criticism to performances by more than 30 area groups. Last night the festival culminated in a company showcase that proved to be a cross section of Washington dance -- from the cutting edge of the new to the more populist and commercial.

Of particular interest was the Dance Construction Company's tantalizing excerpt from Maida Withers' "Laser Dance," which is to be premiered in its entirety in June. Withers, who often collaborates with other performing and visual artists, is working in "Laser Dance" with argon laser art by Rockne Krebs and a digitally synthesized score by Bob Boilen.

Last night's performance of "Quest," the 14-minute opening section of Withers' evening-length work, was given sans laser art, allowing for a concentrated view of the dance itself.

The opening of "Quest" sees dancers in high-tech translucent plastic suits and goggles pour through a break in the backdrop in a seemingly endless stream. The effect is that of the visual trickery of a Mo bius strip as the same dancers appear again and again, their limbs slicing the air in sustained arcs. As the section ends, the windmilling of the limbs gradually breaks down into an intricate tracery of quick, delicate footwork.

Last night's program was also the last area appearance by Cathy Paine before the choreographer moves to Los Angeles. She and Helen Hayes performed Paine's "Brake," which a change of costume transmuted from its original playful commentary on Johann Strauss and the waltz into an intriguingly odd and sexually ambivalent gloss on both old Viennese and contemporary manners.

The Saturday Company performed a tightened version of Diane Floyd's "Aviary." The piece is still overly long and underdeveloped, but it was nonetheless an excellent setting for the exceptional passion and polish of dancer Vivian Kaufman.

The Claudia Murphey Dance Company, a strong group of disciplined and accomplished performers, danced Murphey's "From Here to There" and "Private Matter," works that are solidly crafted but lack depth under their surface shine.

The resident group from Joy of Motion, the Ava/Teri Dance Theatre, offered excerpts from Robert Teri's "The Bomb '85," aptly described by an audience member as "Saturday Night Fever meets Armaggedon." Michelle Ava's "Eurythmics Suite," while not as offensive, used its epic length to no discernibly positive effect.