We described the relative survival of thyroid cancer cases diagnosed in Europe during the period 1990-1994 and analysed time trends in relative survival during the period 1983-1994 using the EUROCARE-3 database. Relative survival of thyroid cancers is one of the highest amongst cancer sites, with age-standardised relative survival rates of 74% in men and 82% in women over the period 1990-1994, with marked differences between countries. The higher relative survival rates are observed in Scandinavian countries and the lower rates are observed in the UK and the countries of Eastern Europe. Relative survival is higher in women than in men, and decreases with age whatever the histological group. There are significant differences in relative survival according to histological type. Relative survival has slightly increased over the period 1983-1994 only when all histological types have been considered together. Time trend was, however, non-existent when the different histological groups were taken into account except during the most recent period of observation. One possible explanation for the differences in relative survival between countries and sex may probably be found in the changes in thyroid classification and diagnosis techniques. When these changes are not homogeneous, the distribution of thyroid cancers by histology and by stage at diagnosis may be very different. The only way to understand these differences is to conduct specific studies including a description of stage at diagnosis, diagnosis procedures used for staging and details of treatment.