Transthyretin and albumin in lumbar cerebrospinal fluid (CSF) and in serum were repeatedly assessed in 40 patients with acute leukemias or high grade non-Hodgkin's lymphomas. The patients were divided into 3 groups. Group I-5 individuals with clinical manifestations of leukemic or lymphomatous meningosis; Group II-33 cases with no clinical data of central nervous system involvement by neoplasm (leukemia/lymphoma); Group III-2 patients in whom extramedullary solid leukemic or lymphomatous infiltrations were diagnosed. It was revealed that blood-brain-barrier dysfunction due to neoplastic infiltration of leptomeninges went with an increase of albumin blood-CSF barrier dependent- and with decrease of blood-CSF barrier-independent transthyretin concentrations. In patients with extramedullary tumors an evident increase of albumin and total-CSF transthyretin and no blood-CSF barrier-independent transthyretin concentrations below the tumor location were observed. It can betray a complete block of the vertebral canal subarachnoid space below the neoplastic compression of the spinal cord. Cytostatics application, either general or intrathecal, did not influence the CSF albumin and transthyretin levels.