Records of 138 patients with leukemia diagnosed between 1955-1974 in Olmsted County, Minnesota, and 276 controls were examined for the occurrence of prior malignancies and hematologic diseases. No significant excess of malignancy was observed when all types of malignancy and all types of leukemia combined were considered. When they were analyzed separately, however, a fivefold increase in the risk of prior skin cancer was found in patients with chronic lymphocytic leukemia. Because of the relatively small numbers, this difference is of borderline statistical significance. The presence of prior hematologic disorders was also examined, and the findings are discussed.