Producing an extracellular alkaline lipase, this isolate JM123 was identified as a Pseudomonas aeruginosa strain from the results of the analyses of its morphological, biochemical and physiological properties. This strain showed the highest productivity of alkaline lipase when grown at pH 9.0 and 30C for 13-20 hours in the medium of 2% starch, 1% soytone, 0.5% peptone and 1% MgSO4.7H2O. However, this enzyme was greatly repressed when grown in the glucose containing medium. The culture broth was fractionated by the order of the ammonium sulfate precipitation, Sephadex G-200 gel filtration, DEAE-cellulose column chromatography, and Sephadex G-150 gel filtration.