Previous studies using somatic cell hybridization of highly metastatic and nonmetastatic rat prostatic cancer cells demonstrated that the resultant hybrids were nonmetastatic if all of the parental chromosomes were retained. Somatic hybrid segregants which underwent nonrandom chromosomal losses reexpressed high metastatic ability. These results demonstrated that there are gene(s) the expression of which can suppress metastatic ability of prostatic cancer cells. To identify the location of homologous gene(s) in the human, specific human chromosomes were introduced into highly metastatic rat prostatic cancer cells using the microcell-mediated chromosome transfer. Introduction of human chromosome 11 into highly metastatic rat prostate cancer cells results in suppression of metastatic ability without suppression of the in vivo growth rate or tumorigenicity of the hybrid cells. Spontaneous deletion of portions of human chromosome 11 in some of the clones delineated the minimal portion of human chromosome 11 capable of suppressing prostatic cancer metastases as the region between 11p11.2-13 but not including the Wilms' tumor-1 locus.