A complete family investigation was made for 598 cases of retinoblastoma and details of any associated congenital malformations were recorded. Associated malformations were found in seven cases, four of which were cleft palate. There was a highly significant difference between the frequency of cleft palate in our cases with retinoblastorna and the frequency in the general population.This result supports the hypothesis that cases of retinoblastoma with associated congenital malformations are caused by germinal mutations.