Several studies have indicated that in prostate cancer, frequent aberrations take place in several genomic regions. In the present study, we have analyzed allelic losses in chromosome 16 region q in 50 prostate cancer specimens of various histological grades. The most frequently deleted region was located at 16q23-16q24.2 between loci D16S504 and D16S422. The highest percentage of loss of heterozygosity (LOH) at 16q was also found within this area at loci HSD17B2 and D16S422 located at 16q24.1-q24.2. The LOH at 16q24.1-q24.2 was significantly associated with clinically aggressive behavior of the disease, metastatic disease, and higher tumor grade. Of the metastatic diseases, 83% showed LOH, whereas only 40% of the nonmetastatic diseases were found to show it. Similarly, LOH was found in 76% of the clinically aggressive diseases and in 33% of the nonaggressive diseases. The data suggest that a potentially important gene associated with prostate cancer progression is located close to 16q24.1-q24.2.