Endogenous levels of the polyamines putrescine, spermidine, and spermine have been examined in the 10(6) m/s2 supernatant of different lobes of the rat prostate and in the seminal vesicles of castrates, androgen-stimulated castrates, and intact controls. Content of the polyamines varied between the lobes, with spermidine highest in intact animals. After castration, the content of polyamines fell significantly in all lobes but the coagulating gland (CG). Spermidine levels were highest, except in the lateral prostate (LP) and CG, where the content of putrescine was highest. In castrated animals treated with testosterone propionate for 72 h, the amount of the three polyamines examined increased dramatically in the ventral prostate (VP) and moderately in the CG and seminal vesicle (SV). Concerning individual polyamines, spermidine increased significantly in all lobes, while putrescine increased significantly only in the two saccular parts of rat prostate, i.e., CG and SV. Spermidine content decreased significantly in the DP. Major differences in the content of the three polyamines--putrescine, spermidine, and spermine--in the various tissues studied have been found. Moreover, distinct differences among intact, castrated, and testosterone-treated castrated animals have been revealed.