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Trypsin was isolated from pyloric caeca of European seabass (Dicentrarchus Labrax) by ammonium sulphate fractionation (30-60%) and size exclusion (Sephacryl S 200) gel filtration chromatography. The enzyme was purified at a rate of 52.71 fold with a yield of 8.60%. The molecular weight of the enzyme was estimated using a low molecular weight marker (Sigma Low Range M3193) and wide molecular weight marker (Sigma Wide Range S8445). The molecular weight of the purified trypsin was estimated to be 24 kDA by sodium dodecyl sulphate-polyacrylamide (SDS-Page) gel electrophoresis, which showed only one band in bromophenol blue staining. The optimum temperature and pH for the trypsin activity were 55 °C and pH 8.0, respectively. The enzyme was extremely stable in the pH range of 7.0-10.0 and highly (70%) stable up to 50 °C after 30 minutes incubation. Na-Benzoyl-L-arginine 4-nitroanilide hydrochloride (BAPNA) was used as a substrate for all activity and stability analyzes. Data of the study showed that temperature and pH factors that significantly affect trypsin enzyme activity. [ABSTRACT FROM AUTHOR]