SUMMARYReports in the literature indicate that white light inhibits aflatoxin production. We studied the effect of continuous white light on the production of aflatoxins and several anthraquinone pigments by wild type and mutant strains of two species ofAspergillusgrown in a liquid defined medium. No light inhibition of these secondary metabolites was observed. However, continuous white light did inhibit the formation of sclerotia in 10 of 13 strains cultured on potato dextrose agar. An action spectrum was obtained for four strains, indicating that wavelengths in the blue-green region were effective in the inhibition of Sclerotium formation. Since the sclerotia of aflatoxigenic fungi contain a potent tremorgen, dark-grown cultures of these molds may present a double toxigenic threat.