1. Family history, careful examination of both parents’ retinas, cytogenetic analysis if the tumor is associated with other malformations, mutation identification. Advise the parents of the risk, but point out that a future child could be examined immediately after birth and at short intervals for some time to make sure that if tumors develop, they are detected and treated early. The parents should be informed of the risk of disease in subsequent pregnancies, the availability of prenatal diagnosis, and the impact of the disease should it recur. 2. Colorectal cancer seems to require a number of sequential mutations in several genes, a process that may take longer than one (in hereditary) or two (in sporadic) mutations in the retinoblastoma gene. Age dependence may also refl ect the number, timing, and rate of cell divisions in colon cells and in retinoblasts.