Meningeal leukemia (ML) is a well-known and rather frequent complication of leukemia especially since the advent of chemotherapy. The first report of neurological complications of leukemia was in 1823 by Burnsl. Before leukemia chemotherapy, there had been only sporadic and relatively few case reports. However, since 1948, the incidence of meningeal leukemia has increased to where it is now one of the most frequent complications of the disease. This review will discuss in depth the pathology, clinical characteristics, and results of treatment of meningeal leukemia. An attempt will be made to assess the relative values of different modes of therapy and suggest new ones in light of animal studies and theoretical models for meningeal leukemia, and to define what parameters are necessary in evaluating the results of therapy, which would be helpful in future studies. This is especially cogent since many of the more recent chemotherapy proto­ cols are utilizing combinations of radiotherapy and intrathecal therapy both in treatment of meningeal leu­ kemia and as prophylaxis against its development.