The epidemiological evidence from the most highly 2,3,7,8-TCDD-exposed cohorts studied produces the strongest evidence of increased risks for all cancer combined, along with less strong evidence of increased risks for cancer of particular sites such as non-Hodgkin lymphoma, soft-tissue sarcoma and lung cancer. The relative risk for all cancer combined in the most highly exposed and longer-latency sub-cohorts is 1.4. While this relative risk is not likely to be explained by confounding, this possibility cannot be excluded. It should be borne in mind that the general population is exposed to 2–3 orders of magnitude lower levels of TCDD than those experienced by the equivalent lifetime dose in the industrial populations examined or the population of Seveso.