This is a clinical, epidemiologic, genetic, and laboratory study of individuals and families at high risk of cancer and selected tumors to investigate the genetic susceptibility and environmental exposures which may alter cancer risk. Families with multiple members who have an unusual pattern or number of cancers or tumors are evaluated clinically. This evaluation is specific for the type of cancer or tumor predominant in the family in order to determine the affection status of each individual for genetic epidemiologic studies. Genetic and environmental risk factor information specific for the tumor type is obtained.