Given the importance of prostate cancer in African American families and the fact that the family history is a significant risk factor for disease in this racial group, we set out to study a set of multiplex prostate cancer families for linkage to five previously reported prostate cancer susceptibility loci: namely HPC1 at 1q24–25 (MIM 601518) (Smith et al, 1996), PCAP at 1q42.2–43 (MIM 602759) (Berthon et al, 1998), CAPB at 1p36 (MIM 603688) (Gibbs et al, 1999), HPC20 on chromosome 20 (Berry et al, 2000b), and HPCX at Xq27–28 (MIM 300147) (Xu et al, 1998). Here, STX1A is linked to prostate cancer.