It is almost axiomatic that chronic lymphocytic leukemia (CLL) is not caused by ionizing radiation. This assumption has been challenged recently by a critical re-appraisal of existing data. A recent paper implicated radon exposure in Czech uranium miners as a possible cause of CLL and in this issue of Leukemia Research the first paper examining the incidence of CLL among those exposed to radiation from the accident at the nuclear power plant in Chernobyl is published. It suggests that CLL occurring among the clean-up workers was of a more aggressive form than is normally seen in the community.