Isaac Stern and Eugene Istomin are two of the world's most distinguished Beethoven players, and their concert last night at the Kennedy Center Terrace Theater of three of the sonatas for violin and piano was as distinguished as listeners had every reason to expect.

For years, Stern and Istomin have been playing the 10 violin sonatas together, and by now the interpretive profiles of their performances are fully in focus, from the grand sweep of the lines to the subtlest matchings of phrase endings and dynamics.

The chance to hear them now arose from two special circumstances. One is that their interpretations are at peak mettle because they have just recorded eight of the set for CBS and will tape the remaining two sonatas next week at the Library of Congress. This coincided with the first benefit concert at the Terrace for the $1 million Abe Fortas Fund, named in honor of the late Supreme Court justice, which will endow chamber music concerts at the Terrace. Fortas was a founder of the Kennedy Center and was the prime mover in creating the Terrace Theater.

The heart of the program last night was an enormously fiery, assured version of the most famous of the sonatas, the "Kreutzer." From the opening chords that the violinist plays alone, done with stunning accuracy and power by Stern, the first movement blazed along magnificently. And the finale sailed away at a considerable clip.

Other especially memorable moments: Istomin's wonderfully pearly tone and evenness in the elegant first movement of the Second Sonata, Op. 12, No. 3; Stern's ethereally soft tone in the second movement of the "Spring" sonata, and the dizzying steadiness of both players in the finale of the "Spring."

If there was a rare slip on a note or two, it was almost to be expected. Stern and Istomin play with such high-risk intensity that these are the little sacrifices that are the cost of their enormous impact.

A black-tie buffet for about 200 persons was held after the concert.