1. Chromobacterium violaceum (strain BB-78 isolated in Brazil) produces violacein, a substance potentially useful in phototherapy and with antibiotic and trypanocide activity. Culture conditions were optimized for the production of violacein and changes in nutrients, temperature and pH were correlated to cellular growth. 2. Methionine was the only absolute requirement for growth. Alanine, arginine, tryptophan and vitamin B12 stimulated growth and the microorganism utilized both the D and L forms of methionine. L-Tryptophan and its metabolites were important as a carbon source for violacein production and bacterial growth. 3. The highest yields of violacein were obtained by incubation in liquid medium and in the absence of light at pH 7.0 and 28 degrees C for 24 h.