Epidemiologic studies have shown that hereditary forms account for approximately 10% of all prostate cancers. The identification of several susceptibility loci harboring predisposing genes indicates the genetic heterogeneity of prostate cancer. The conflicting results of different linkage analyses may be explained by a varying contribution of each locus within different family collections and reflect differences of allele frequencies across different populations. In the present study we recorded the incidence of familial prostate cancer in Germany and performed descriptive analysis of the epidemiological data. In spite of a significant ascertainment bias, only 19% of all prostate cancers were familial. In 94% of families there were three affected relatives at most. Large prostate cancer families with at least five affected persons were rare (2%). Descriptive analysis revealed that only 42% of all pedigrees followed an autosomal-dominant pattern of transmission; the other pedigrees showed an X-chromosomal or recessive mode of inheritance. These data confirm the genetic heterogeneity of hereditary prostate cancer and imply that previously published epidemiological data cannot be transferred to the German population.