This study investigated the influence of ionic strength, liposome net charge and enzyme concentration on the immobilization of chymotrypsin in liposomes obtained from proliposomes. Depending on ionic strength and chymotrypsin concentration, immobilization efficiencies (IE) as high as 96 and 68% were obtained for liposomes prepared with Pro-lipo(R) 3045 S and Pro-lipo(R) 3080 S respectively. Increasing ionic strength and enzyme concentration resulted in a decrease in IE for both types of liposomes, and this was more pronounced for ionic strength. Relatively high amounts of chymotrypsin were found to be immobilized on the surface of the liposomes. Hydrophobic interactions between chymotrypsin and the hydrophobic tails of the phospholipids during liposome formation were probably responsible for this phenomenon.