We wish to initiate a screening program oriented specifically to in vivo visualization of the human prostate by scanning with the Anger scintillating camera subsequent to administration of a gamma emitting compound that mimics the prostate binding characteristics of 17 beta- hydroxy-5-alpha-androstan-3-one. We will synthesize the 19-iodo analogue, radioiodinate by exchange procedures, and determine its biological profile by rat androgen bioassay, and rat and dog prostate binding characteristics compared to 5 alpha-DHT. This program is oriented specifically to the early diagnosis of human prostatic cancer with increased accuracy of staging. It is also for the purpose of outlining the prostate area, determine the per cent isotope uptake, thus permitting the physiology of the prostate to be studied. Additionally the effects antiandrogenic compounds exert on the prostate binding characteristics of 19-iodo-5-alpha-DHT will be studied, with the view that benign prostatic hyperplasia may be medically treated. It may be possible to treat prostatic cancer with 19-iodo-5-alpha-DHT after radioiodination widh I131-by in situ perfusion.