Development of free fatty acids (FFA) and subsequent deterioration of palm oil quality can be attributed to lipase, an active hydrolytic enzyme present in the mesocarp of oil palm fruit. A histochemical method was used to localize this enzyme in the mesocarp. FFA released from endogenous glycerides were precipitated as lead salt. The deposits were located on the membranes of oil bodies. Enzymatic activity in the mesocarp was also studied under different conditions of fruit storage: ambient temperature, freezing, etc. The enzyme was active after freezing but less active under ambient conditions of fruit storage. Investigations on fruit development indicated that the enzyme activity started appearing between 16–20 weeks after anthesis (WAA) which synchronized with the beginnning of lipid formation. These histochemical studies were supported wity biochemical data on FFA.