We analysed 39 prostatic carcinomas for loss of heterozygosity on chromosomal arms 8p, 10q, 16q, 17p and 18q and for mutations in the p53 anti-oncogene. Loss of heterozygosity (LOH) on 8p was detected in one out of 5 informative tumors, LOH on 16q in 3 out of 21 tumors, LOH on 17p in 2 out of 18 tumors, and LOH on 18q in 2 out of 17 tumors. No deletions were observed on 10q in 14 informative tumors. p53 alterations occurred in 3 out of 38 examined tumors, comprising two point mutations and a small deletion. Chromosomal deletions and p53 mutations were confined to locally invasive prostatic carcinomas, suggesting that they are associated with the progression of some prostate cancers rather than with tumor initiation.