Organic nitrogen sources were more readily utilized than inorganic nitrogen sources by three strains ofClaviceps purpurea. Glucose, fructose, mannose, cellobiose, and sucrose were readily utilized, but not xylose, ribose, mannitol, maltose, starch, powdered cellulose, carboxymethyl cellulose, or methyl cellulose. Carbon dioxide was required for initiation of growth. An exogenous supply of biotin was required for growth in a medium containing glucose, ammonium succinate, and minerals. This requirement could be nearly replaced by equimolar amounts of biotinL-sulphoxide and biocytin. Desthiobiotin slightly replaced biotin but homobiotin, norbiotin, oleate, aspartate, pimelate, and Tween 80 were inactive. Oleate and aspartate stimulated early growth.