Eighteen of 41 isolates of Clavkeps purpurea produced a detectable quantity of the ergot alkaloids under standard conditions. Large differences in yield indicated that strain differences existed. There was no correlation, however, between the capacity to produce alkaloids and either the species of host from which the culture was isolated or the pigmentation of the culture.The time of incubation and the composition of the medium were important in determining whether natural light stimulated or inhibited the synthesis or accumulation of ergot alkaloids.Commercial galactose, which was contaminated with glucose and lactose, was the most efficient carbon source examined, but the rate of synthesis was markedly reduced if the galactose was purified before use. The activity of commercial galactose could be replaced by a mixture of pure galactose and glucose but not by a mixture of galactose and lactose. A strong interaction existed between the concentration of commercial galactose and phosphate. Ammonium succinate, soybean meal, urea, and yeast extract were the most efficient nitrogen sources examined. L-Tryptophane could not serve as a nitrogen source for growth but when added as a supplement influenced alkaloid production. Succinic but not citric, tartaric, phosphoric, acetic, or sulphuric acid could be used successfully to adjust the initial pH of the production medium. The replacement culture technique did not shorten the incubation time required for alkaloid production.Production of alkaloid, growth, and consumption of carbon and nitrogen proceeded at a steady rate until the 43rd day when the rate decreased markedly. Organic nitrogen but not polysaccharide was secreted into the medium.The total yield and the rate of alkaloid synthesis was influenced by the size of the inoculum and by the nature of the agent used to suspend the inoculum, but not by the number of times the inoculum was washed. The rate of production was very slow if the inoculum source was not homogenized.