Black American men have a higher incidence of cancer of the prostate (CAP), multiple myeloma, and lung cancer than do white American men (discussed by Lyn et al.1993a). The basis for these differences no doubt includes environmental influences, because American blacks have also been found to have a higher incidence of CAP than do African blacks. However, genetic factors may play a role as well. For example, Lyn et al. (1993a) reported an increase in the frequency of an allele of the poly(ADPribose)polymerase (PADPRP) pseudogene locus onchromosome 13 in black Americans with CAP, suggesting the presence of a disease-susceptibility locus. Since only nine CAP patients were studied, proof of the significance of the finding for the general population of black Americans will rely on independent replication of the result and studies with larger sample sizes. We have doubled the number of black American CAP patients studied at the PADPRP pseudogene locus on chromosome13 and compared them with white Americans with CAP, along with reference samples. In addition, we have determined allele frequencies by using a larger number of white individuals, from the CEPH reference pedigree resource, and a larger number of black Americans than previously reported, which may reflect more accurately the allele frequencies in these populations. We also find a statistically significant association between an allele at the PADPRP pseudogene locus and CAP in black Americans; however, it is not the same allele reported by Lyn et al. (1993a). Furthermore, we tested CAP tumorDNA for chromosome 13 PADPRP pseudogene region deletions. In contrast to the report of Bhatia et al.(1990), we found no evidence for deletions that would suggest the presence of a tumor-suppressor gene in this region of chromosome 13.