Production of lovastatin and microbial biomass by Aspergillus terreus ATCC 20542 were influenced by the type of the carbon source (lactose, glycerol, and fructose) and the nitrogen source (yeast extract, corn steep liquor, and soybean meal) used and the C:N mass ratio in the medium. Use of a slowly metabolized carbon source (lactose) in combination with either soybean meal or yeast extract under N-limited conditions gave the highest titers and specific productivity (similar to0.1 mg g(-1) h(-1)) of lovastatin. The maximum value of the lovastatin yield coefficient on biomass was similar to30 mg g(-1) using the lactose/soybean meal and lactose/yeast extract media. The optimal initial C:N mass ratio for attaining high productivity of lovastatin was similar to40. The behavior of the fermentation was not affected by the method of inoculation (fungal spores or hyphae) used, but the use of spores gave a more consistent inoculum in the different runs. (C) 2003 Elsevier Inc. All rights reserved.