It is well known that microorganisms are able to grow and transform vegetable oils due to the excretion of lipase, which renders the lipid substrates available to cells. The purpose of the present study was to screen for lipase production from used olive and sunflower frying oils. From the 47 strains of bacteria and yeast screened, the genera Pseudomonas, Bacillus, Candida, Rhodococcus, and Staphylococcus grew on the waste oils and produced lipolytic activity. The highest producers were Pseudomonas sp 3AT (2748 U/L) and Pseudomonas aeruginosa ATCC 111 (1703.8 U/L). (C) 2000 Elsevier Science Inc. All rights reserved.