It was a very good year for commercial theater in the 52 weeks ending May 29, according to Variety, the trade paper.Broadway and "road" shows played a total of 2,335 weeks during the year, the second highest total since Variety started tabulating the figures in the 1938-39 season. All this resulted in a combined gross of $176,033,391, by far the highest in history, although some of this can be explained by inflation-fed ticket prices.

Among the "road" cities, Washington led the list in the number of shows - 34 - but placed a distant second to Los Angeles in the total gross - $10,980,381 compared to L.A.'s $23,211,077 gleaned from 30 shows. These statistics count commercial productions only - shows that play the Kennedy Center, the National or Ford's, for example, but not those at Arena or the Folger.

This does not mean Broadway is now a bed of roses. Among the Broadway shows that opened during those 52 weeks. Variety found only 12 "success," compared to 40 "failures" (including "tryout casualties") and 11 shows with "status not yet indicated."

Turning to noncommercial theater, the National Endowment for the Arts has announced that the theaters it helped support over the past year gave more than 34,000 performances of 1,700 productions to an audience of almost 12 million. That's about twice the number of performances reported in the Variety survey and many times more the number of productions. But the attendance figures are probably about even: on Broadway the figure last season was 8,815,095, and "road" attendance figures were not available.

The National Endowment distributed $5.9 million to theater groups last year. The largest single grantwas the $200,000 to Arena Stage, which was supplemented by $56,000 to Living Stage, an adjunct of Arena.

Turning away from the commercial theater and even the merely noncommercial theater to what we might almost call the anticommercial theater, we find the New Theater Festival still in full swing at the University of Maryland, Baltimore County.

Tonight is the last night to catch South Africa Black 77, a company of five South Africans from the riot-wracked city of Soweto. Last night The Dance Exchange joined the Living Stage in representing Washington at the festival. Dr. James Hindman of American University is also there, conducting workshops but not public performances.

The festival continues through Sunday,, with details at 301-455-3193.

Shady Grove's new manager is Stephen H. Arnold, formerly manager of the Westbury Music Fair (1970-72) and the Valley Forge Music Fair (since 1972), both successful branches of the Guber-Gross organization that runs Shady Grove . . . The recently reopened Waaay Off Broadway caberet offers a three-night stand of "The Boys in the Band" beginning Friday . . . "The Doctor in Spite of Himself," Moliere's heavily language-oriented play, is being presented in sign language through Saturday by the Model Secondary School for the Deaf, on the Gallaudet campus. Readers are unhand too . . . The Virginia Museum Theater Repertory Company in Richmond will not have an artistic director next season, in the aftermath of former director Keith Fowler-s resignation protesting censorship. Guest direstors will be imported for each production and for tacit tryout for the top job.