Under the aegis of EUROCARE, a European Union project to assemble survival data from population-based cancer registries and analyze them according to standardized procedures, we have investigated and compared colon-cancer survival in 10 European countries. We analyzed 68,283 colon-cancer cases diagnosed between 1978 and 1985 and followed for at least 6 years. After calculating relative survival, putative factors prognostic for survival were investigated by univariate and multiple-regression analyses. Important intercountry colon-cancer survival differences exist within Europe, which are not explained by methodological differences, nor by demographic confounders. In patients aged 60 to 69, the mean European 5-year cumulative relative survival was 40%. Switzerland, Finland and The Netherlands had significantly higher 5-year relative survival, while one area in the UK and Cracow in Poland had significantly lower survival than this European estimate. Prognosis improved over time: from 1978 to 1985, the risk of death was reduced by about 4% per year in all countries studied. Age at diagnosis is inversely related to prognosis. Differences in health provision and hence in quality of care and stage at presentation seem largely responsible for the differences in colon-cancer survival found in the EUROCARE countries.