Ventral prostates from adult Sprague-Dawley rats were removed at intervals during the first 2 weeks postcastration. Incubation of tissue with 3H-uridine and 3H-leucine was performed to determine the incorporation rate of radioactivity into the RNA and protein fractions respectively. Prostatic wet weight and 3H-leucine incorporation rate into prostate protein diminished postcastration, whereas 3H-uridine incorporation rate remained relatively high. The data suggest that RNA synthesis is relatively active in comparison with other parameters during regression.