This study of a 30-year population-based dataset investigates further an earlier observation that the incidence of sporadic bilateral retinoblastoma appeared to be increasing in recent years in the West Midlands Health Authority Region (WMHAR). Stringent measures were applied to ensure complete ascertainment of all cases of retinoblastoma in children in the region, resulting in a total of 117 cases diagnosed during the period 1960-89 in the WMHAR. Hospital case notes were abstracted and follow-up data obtained. Incidence rates were calculated. The overall incidence remained constant over the 30-year period, but that of sporadic bilateral tumours increased, with a corresponding decline in familial cases. There was a statistically significant excess seen in Asian children.