The activity and electrophoretic mobility of leucine amino peptidase (LAP) were assessed in the sera of 100 patients with different clinical stages of Schistoisoma haematobium infection as well as in 20 samples of ascetic fluids obtained from patients with bilharzial hepatosplenomegaly associated with Ascities matched with 20 healthy adult males sample as control. Generally LAP activity was significantly higher in all patients. The activity of serum LAP showed a progressive rise with the advance in the clinical condition. The highest level was encountered in the sera of patients with cancer of the urinary bladder and liver metastasis. leucine amino peptidase was considerably found in the ascetic fluid. The ratio of the activity of LAP in the ascetic fluid to its activity in the serum of the same patients was 1:4.5 where the enzyme diffuses from the blood to the ascetic fluid. The enzyme detected by electrophoresis, in serum or ascetic fluid LAP migrated as a single component in the 1- globulin fraction. The results are discussed and compared with those in the literature.