Nuclear envelope peptides of the rat ventral prostate in the molecular weight region 18,400 to 19,400 show marked androgen dependence. After castration these peptides disappear. Re-administration of testosterone restores them. They were not extracted by 0.1 M NaCl or 5% HClO4 but were partially extracted by 0.35 M NaCl and 1% Triton. These peptides were not present in rat liver nuclear envelopes. As these androgen-dependent non-histone peptides have similar characteristics to androgen-dependent peptides identified in the prostate nucleus, we conclude that the nuclear peptides are at least partially localized to the nuclear envelope.