The aim of this register-based follow-up study was to evaluate the long-term cumulative incidence of second primary tumors (SPT) among survivors of hereditary retinoblastoma, with special interest for the incidence of pineoblastoma in retinoblastoma patients born after 1970. The Dutch Retinoblastoma Register was completed and updated: in the period 1945-1994, 639 retinoblastoma patients were registered. The vital status of each patient was obtained from the municipal registries and the Central Office of Genealogy. SPT were traced and histopathologically confirmed. Survival curves and cumulative incidence of SPT were calculated by the Kaplan-Meier method. The survival of patients with hereditary retinoblastoma was significantly shorter than that of patients with non-hereditary retinoblastoma. The cumulative incidence of SPT in hereditary patients was 3.7 and 17.7% at the ages of 10 and 35 years, respectively. Long-term follow-up revealed a high proportion of melanomas (7 melanomas out of 28 SPT). In the sub-cohort of the hereditary-retinoblastoma patient group born after 1970, the cumulative incidence of pineoblastomas at the age of 5 years was 9.3%. Our results suggest that patients with hereditary retinoblastoma should have careful follow-up, and procedures for diagnosing SPT and pineoblastomas at an early and potentially treatable stage should be developed.