The survival of patients with thyroid cancer was analysed using population-based EUROCARE II data from 1978-1989 (trends in survival) and 1985-1989 (cross-sectional comparisons between areas). The data consisted of 7504 patients and covered 37 cancer registration areas in 17 European countries. In 90% of the patients the diagnosis was histologically confirmed. The prognosis of patients with thyroid cancer was relatively favourable. The overall 5-year relative survival rate was 72% for men and 80% for women. Substantial variation in this 5-year rate was observed between countries ranging from 59 to 83% in men and from 72 to 84% in women. Higher than average survival rates were observed in Finland, Iceland, The Netherlands and Sweden. Countries with lower than average rates were Denmark, England, Estonia, Slovakia, Slovenia and Poland (women). Elderly patients had lower survival rates than the younger ones. Time trends in survival (which could be analysed only in selected countries with sufficient numbers of cases) were irregular but generally showed slight increases compared with rates in 1978-1980. Different distributions in the histological subtypes of thyroid cancer is one plausible explanation for the variation in the survival rate. Other likely factors contributing to this are differences in the stage distribution and varying efficacy of treatment. The EUROCARE II data did not permit specific analyses of the roles of various prognostic factors.