The first 7 cases of histologically and cytochemically confirmed Burkitt's lymphoma have recently been studied in Cuba. Some of them presented with facial bone involvement and high anti-Epstein-Barr virus (EBV) antibody titers characteristic of endemic African cases. Others showed features of nonendemic cases. The distribution of patients in these two groups may be in relation to the behavior of the healthy Cuban population with respect to the EBV virus.