Regional and temporal patterns of variation in the incidence of cancer of the oesophagus in the Central Asian republic of Karakalpakstan were analysed. Karakalpakstan (population about 1200,000) is an area with high rates of this disease. Incidence data within regions (data from 1988-1989), ethnic groups (data from 1987-1989) and calendar periods (data from 1973-1987) were available for analysis, with corresponding official population estimates. No significant difference was observed between rates in urban and rural environments, although significant regional variation was observed (P less than 0.05). The highest rate observed was in the Muinak, the northern region, with world age-standardized rates (ASR) of 125.96 for males and 150.65 for females. There was a very significant difference among ethnic groups (P less than 0.001). The ethnic group with the highest incidence was the Kazakh people, with an ASR of 68.0 in males and 86.3 in females. Incidence in the republic as a whole declined in the period from 1973 to 1987. Incidence of cancer of the oesophagus is still high in Karakalpakstan, despite the decline. Incidence is likely to be strongly related to factors associated with region of residence and with ethnicity.