A fast parallel algorithm for the recognition of ultrametrics is prese
nted. Its time-processor product is of the same order as the time boun
d of the known sequential algorithm of Culberson and Rudnicki [Inform.
Process. Lett., 30 (1990). pp. 215-220] (compare also [SIAM J. Disc.
Math., 3 (1990), pp. 1-6] and [Quart. Appl. Math., 26(1968), pp-607-60
9]. By the same way, tree metrics also can be recognized.