SUMMARYTryptophol (TOL) and indolelactic acid (ILA) were synthesized by isolates ofCryptococcus neoformansin a synthetic medium containing tryptophan as the sole nitrogen source. The compounds were produced in maximal amounts at 48 to 72 h of growth at 37 C. Trace amounts of indolepyruvic acid (IPA) were found in acidic extracts, indicating that IPA is an intermediary in the conversion of tryptophan to TOL and ILA. Of all theCryptococcusspecies tested, only isolates ofC. neoformanssynthesized both indole compounds. Thus, the two products—which can be readily isolated and identified by gas-liquid chromatography—could serve as markers for distinguishingC. neoformansfrom other species ofCryptococcus.