A study on the dermatomycoses of Puerto Rico made between 1930 and 1949, including 839 observations, disclosed eight different types of ringworm. Tinea pedis led the list with 327 cases, or 39% of the total; tinea unguium was next with 202 cases (24.1%); and this was followed, respectively, by tinea corporis with 172 cases (20.5%); tinea capitis with 97 (11.6%); candidiasis with 18 (2.1%); tinea nigra with 11 (1.3%); tinea nodosa with seven (0.8%); and tinea barbae with five (0.6%). The mycologic flora associated with these infections consisted of 11 fungus species as follows:Trichophyton mentagrophytes, 350 isolates (41.7%) among the total of 839 fungus specimens collected;T rubrum, 304 isolates (36.2%);T tonsurans, 70 (8.3%);Microsporum canis, 42 (5%);Epidermophyton floccosum, 26 (3.1%);Candida albicans, 18 (2.1%);Cladosporium wernecki, 11, (1.3%);M gypseum, nine (1.1%);Piedraia hortai, five (0.6%);Trichosporum beigelii, two (0.2%); andM audouini, two (0.2%). The above data have been carefully analyzed and evaluated from different points of view, and I have included in the discussion personal remarks, comments, and experiences related to the subject.