This is a multidisciplinary etiologic study targeting families at increased risk of testicular cancer (TC). The goals of this study include: 1) define the clinical phenotype of familial TC; 2) map and clone hereditary TC susceptibility genes; 3) determine if cancers other than TC are part of the familial TC syndrome; 4) determine if the pathology of familial TC differs from that of non-familial TC; 5) create a biospecimen repository for subsequent translational research projects.