The production of alkaline proteases by Bacillus licheniformis ATCC 21415 was studied. The highest yield of alkaline protease was achieved using a mixture of lactose (4%) and glucose (1.5%) as carbon source. An alkaline extracted soybean (6%) and ammonium phosphate (1.2%) mixture was the best nitrogen source. Addition of CaCl2 from 0.01 to 0.07% optimized the production of the enzyme. Adding 1% corn oil to the medium as surfactant led to a dramatic increase of the activity to 20379 U ml(-1). In addition, the activity reached 29554 U ml(-1) when the agitation was increased from 250 to 400 rpm. B. licheniformis 21415 could produce the same amount of protease whether sodium lauryl sulphate (SLS) was added to the medium at 0.15% concentration or not. The enzyme was stable at 50 degrees C for 15 min and lost 48.8% of its activity after 1 h. Polyphosphate slightly inhibited the enzyme activity (3%), but EDTA caused a loss of 22% of the original activity.