The conversion of cholesterol (C) to androstenedione (AD) and androstadienedione (ADD) was influenced significantly by the composition of the cultivation medium. A medium composed of (g/l): glucose, 50; peptone, 20; corn steep solid, 3; supported relatively high AD and ADD outputs. C convertibility was further accelerated when the cultivation medium was adjusted with phosphate buffer with the pH range 5.5-7.38. Supplementation of the medium with 8-hydroxyquinoline or methanol prevented the degradation of the C nucleus with concomitant formation of good AD and ADD yields. (C) 2004 Published by Elsevier Ltd.