The extracts of human prostatic tissue specimens contain oncornavirus-like reverse transcriptase activity. This activity was isolated by banding the tissue extract in an equilibrium sucrose density gradient followed by phosphocellulose chromatography of the lysate of the material banding at a density of 1.14--1.20 g/cc. It was characterised by its utilisation of poly (Cm) as a template and its inhibition by selective inhibitors of viral reverse transcriptase. Human prostatic tissues of three histo-pathologic types--normal, hyperplastic and adenocarcinoma--were examined. One out of four normal, five out of six hyperplastic, and two out of two adenocarcinoma specimens displayed virus-like reverse transcriptase activity.