rather than spontaneous.* The latent period for development of leukemia after radiation varies from 6 months to more than 30 years (46). time studies of the exposed Marshallese are required. Accordingly, life- *A number of hematological examinations for leukemia have been carried out over the years including studies of blood smears for immature forms, basophil counts, and alkaline phosphatase staining, ylelding negative results. We are grateful to Dr. W. Maloney and Ms. Tullin at Harvard Medical School for assisting with these studies. - 24 -