Thirty-six families with tuberous sclerosis (TS) were clinically examined for oral fibromatosis and other previously reported oral anomalies. These consisted of 48 affected persons and 69 apparently unaffected parents and children. Fifty control subjects were also examined. Oral fibromatosis was observed in 56% of patients with typical TS and in none of 9 "atypical" cases. The total prevalence was 46%. Similar lesions were not seen in the control series, and they were rare in the otherwise apparently normal relatives with TS. However, three parents of patients with TS were found to have oral fibromas even though they had no signs of TS. It is suggested that examination for oral fibromatosis should be made in all persons suspected of having TS and in their close relatives, since such examination may identify other unsuspected carriers of the gene within the family.