Lovastatin was produced by solid state fermentation (SSF) using Aspergillus flavipes BICC 5174. Different solid substrates such as wheat bran, bagasse, barley, soybean meal, gram bran, fruits waste and some of their combinations were tested for lovastatin production. Of these substrates, wheat bran was found to be the most suitable substrate yielding 13.49 mg g(-1) dry solid of lovastatin in stagnant beds and 16.65 mg g(-1) dry solid of lovastatin in aerated stiffed beds after 6 days of fermentation. Supplementing the solid substrate with external carbon sources such as sucrose and lactose and nitrogen sources such as urea, ammonium sulphate and ammonium nitrate inhibited lovastatin production. Effect of particle size, moisture content and pH of the substrate was also studied. Wheat bran of particle size ranging from 0.3 to 0.5 mm having moisture level of 60% and pH 5.0 gave the highest yield of lovastatin. The variation in lovastatin production with the depth of substrate bed was studied. Reactor studies were also carried out in a 21 reactor. A yield of 16.78 mg of lovastatin per gram of dry solid was obtained in the reactor under optimized conditions after 6 days of fermentation. (c) 2005 Elsevier Inc. All rights reserved.