Results are reported of a series of assays to determine roughly the cellulolytic activity, as measured by decline in tensile strength of cotton fabric, of certain fungi isolated from textiles and related materials deteriorated in the tropics. The total number of assays was 584. These represent 453 cultures distributed among 45 genera. Of the 453 cultures, 310 are identified to series, species or variety and 143 are detd. only to genus or section of genus. The total of 310 cultures determined beyond generic rank, i.e., the number of spp. or approximate spp., is 91. The great majority are the imperfect stages of Ascomycetes (Fungi imperfecti); a few are perithe-cial and a few represent Mucorales. No Basidiomycetes are involved. Cellulolytic activity is indicated for 41 of the detd. spp., whereas 50 gave negative results.