Leukocyte alkaline phosphatase (LAP) activity in peripheral blood was determined in 113 patients with non-metastatic malignancies, 36 patients with metastatic spread, and 22 individuals who served as controls. The LAP score of the non-metastatic cancer patients was significantly higher (p less than 0.001) than the controls, and the score of the metastatic group was further increased significantly as compared to both control (p less than 0.001) and non-metastatic groups (p less than 0.001). The results of this survey suggest that the level of LAP score in peripheral blood might be used to differentiate between non-metastatic and metastatic disease and might serve as an aid in prognosis of the patients.