There are no known reports of the occurrence of Saprolegnia australis Elliott since its initial isolation (Elliott, 1968). Saprolegnia australis is prevalent, however, in small streams feeding Bradley Creek, Wilmington, North Carolina. The most striking dissimiliarity of the present isolate (UNC-W No. WlOb, ATCC No. 32940) from the type species is sporangium size (FIGS. 1-4). Elliott reported the median primary sporangium length to be 40-80 tm, while those of W-lOb are 189-243 t/m (median 70%). Secondary sporangia in W-lOb, like the type species, usually are short and arise by internal proliferation; but in W-lOb secondary sporangia up to 600 tm in length are not uncommon at the tips of robust hyphae (FIG. 5). In 6-da-old cultures several sporangia exhibited dictyoid spore discharge, a characteristic not noted by Elliott. Although W-lOb is clearly an isolate of S. australis several aspects of its sexual morphology serve to broaden the species concept. Neither the antheridial branches no antheridia are persistent (FIGS. 6-7) while the reverse was true in Elliott's isolates. Fertilization tubes were found in three cases in W-lOb, (e.g., FIG. 8), but none were noted by Seymour (1970) in preserved slides of the type culture. O6spheres are variable in size as in Elliott's isolates, the smaller ones being produced by budding of large o6spheres (FIGS. 9-12). Mature subcentric o6spores of greatly varying sizes thus can be found in the same o6gonium (FIG. 7), but