Scrutiny of the family pedigrees of a population-based series of 176 children diagnosed with Wilms' tumor between 1954 and 1990, along with a review of the literature on the Li-Fraumeni cancer family syndrome, indicate that Wilms' tumor may be an uncommon component of the syndrome and that a small proportion of children with Wilms' tumor may be members of Li-Fraumeni syndrome (LFS) families.