Recently, cytogenetic and molecular biological studies have identified the band 8q24, where the located c-myc gene is commonly amplified in prostate cancer, especially in advanced and recurrent ones. Our objectives in this study were to define the role of c-myc and the gain of chromosome 8 in prostatic carcinogenesis and to evaluate the genetic relationship between prostatic intraepithelial neoplasia (PIN) and carcinomas. We examined a total of 30 specimens, including 9 adenocarcinoma, 6 PIN and 15 benign prostatic hyperplasia (BPH) by Fluorescence in situ Hybridization (FISH). The gain of chromosome 8 identified in 88.8% of adenocarcinomas was associated in metastatic prostate cancer. The most frequent anomaly in PIN and carcinoma was a gain of chromosome 8, and the presence of this anomaly strongly correlated with a high Gleason Score. We believe that the basic mechanism in overexpression of c-myc gene may not be amplification. Our results indicate that the basic mechanism of c-myc gene overexpression may be simple gain of chromosome 8 or gain of ‘’8q’’. Our results agree with findings of other authors that PIN is probably a procurser of carcinoma.