The quantitative determination of indigotin production by the wood-rotting basidiomycete Schizophyllum commune was accomplished by extraction of the pigment with hot acetone followed by colorimetric comparison with an indigotin standard reference curve. Ammonia was the only inorganic nitrogen source which was utilized, but the organism was not limited with respect to organic nitrogen. Growth in a medium containing tryptophane resulted in the production of a still unidentified red pigment. Of the carbohydrates studied D-xylose gave the highest values for the production of mycelium; D-fructose and D-glucose gave the highest values for the production of indigotin; and the sugars D-arabinose, L-rhamnose, L-sorbose, and lactose were not utilized. Strain 130 of S. commune grew best at temperatures below 30cC in an acid medium and pigment was produced in the pH range of from 6.3 to 4.0.