Capabilities of 22 molds were assessed for 11beta-hydroxylation of cortexolone (Reichstein's compound S) to hydrocortisone. The biotransformation capability was compared for solid-state and submerged monocultures of the molds under otherwise identical conditions. A novel rapid color development assay and thin layer chromatography were used to qualitatively establish the ability of the fungi to convert cortexolone to hydrocortisone. These assays were validated and supplemented with data from high performance liquid chromatography to obtain quantitative information on the biotransformation. Nearly all the fungi consumed a significant fraction of the cortexolone fed, but only four (i.e. two isolates of Cunninghamella blakesleeana, C. echinulata and Curvularia lunata) yielded measurable quantities of hydrocortisone. Submerged cultures generally gave significantly greater yield of hydrocortisone compared to equivalent solid-state cultures.