A cholesterol esterase-producing microorganism, strain CES 506, isolated from soil was identified as Aeromonas sp. This strain produce about 0.023 units of cholesterol esterase per ml of culture broth. The cholesterol esterase produced by this strain was purified, 370 fold to homogeneity in an overall yield of 24% from culture broth. The apparent molecular weight was 64, 000, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme showed a high substrate specificity for cholesterylpalmitate and the Km value for the hydrolysis of cholesterylpalmitate by this enzyme were 0.15mM.