Hematopoietic and lymphoproliferative cancer risk among the 3.7 million United States male veterans who use the Veterans Administration (VA) medical system annually was assessed using age-specific incidence curves and cumulative incidence rates. Relative risk comparing the VA with general population risk estimates from the Surveillance, Epidemiology, and End Results (SEER) data were increased significantly for all malignancies examined. The VA sample showed risk increases of 93% for Hodgkin's disease, 20% for non-Hodgkin's lymphomas, 51% for multiple myelomas, and 40% for all leukemias. Among the leukemia subtypes, the observed risk increases were 54%, 23%, 80%, and 46% for lymphocytic, granulocytic, monocytic, and other forms of leukemia, respectively. The large size of the sample and the consistency of risk estimates with two different methods confer validity and strength to these findings. The possible relevance of the high prevalence of tobacco and alcohol use in this population sample to the current findings is discussed and the need for further analytic investigations to explain the increases in risk is emphasized.