Leukocyte alkaline phosphatase score in patients with cerebrovascular disease and in patients with primary and metastatic brain tumors. Leukocyte alkaline phosphatase (LAP) activity in peripheral blood was determined in 54 patients with cerebrovascular disease (CVD), 11 patients with primary brain tumor, and 23 patients with metastatic brain tumor. The LAP score of the primary brain tumor patients (155 +/- 40) was significantly higher (P less than 0.03) than the LAP score for cerebrovascular disease patients (96 +/- 87). The LAP score levels of the metastatic brain tumor patients (251 +/- 55) was significantly higher as compared with both the cerebrovascular disease (P less than 0.001) and primary brain tumor groups (P less than 0.001). The LAP score could serve as an additional, although non-specific, marker to assist in the differentiation between cerebrovascular disease and brain tumors. 