[en] This paper summarises the results of pilot studies carried out to evaluate the feasibility of long-term epidemiological studies of cancer risk among populations exposed to radiation from the Chernobyl accident. These studies demonstrated that it is feasible to carry out a study of radiation-induced risk of specific cancers among 'Chernobyl liquidators' included in the State Chernobyl registries using a case-control approach in Belarus and Russia. Careful large-scale studies of liquidators will provide important information concerning the effects of exposure protraction and perhaps of radiation type in the relatively low dose (0-500 mSv) range. Protocols for case-control studies of leukemia and thyroid cancer risk among liquidators are being prepared in Belarus and Russia. Non-specific studies of cancer risk among the general population exposed in the contaminated regions are unlikely to be informative for radiation risk estimation because of the generally lower doses received by the majority of these populations, the difficulties in estimating these doses and following populations. An exception is the study of thyroid cancer risk in children, the incidence of which has been observed to increase dramatically in the first years following the accident. A careful study appears to be feasible and may provide a unique opportunity to increase our understanding of factors which modify the risk of radiation induced cancer and thus have important consequences for the radiation protection of patients and the general population