We investigated the report of a community cluster of cancers in 33 children, which included two siblings known to have dominantly inherited Li-Fraumeni syndrome and a germline p53 mutation. After defining criteria for inclusion in the cluster, the 12 eligible childhood cancer probands diagnosed between 1980 and 1989 were not excessive (expected, ten cases). The corresponding childhood cancer mortality rates for the community fluctuated between 1950 and 1989 and were not increased overall. However, three additional probands had family histories of childhood cancer that suggested a forme fruste of Li-Fraumeni syndrome. The epidemiological data suggested a geographic cluster of this rare hereditary disorder, but absence of germline p53 mutation in the three other multicase families indicates genetic heterogeneity. Laboratory studies can assist analyses of suspected clusters, although investigations of geographic clusters of hereditary cancers raise complex issues of confidentiality and protection of affected individuals, their families, and the community.