Immunostainable β-endorphin and ACTH are present in the cytoplasm of Leydig cells and in the epithelium of the epididymis, seminal vesicle., and yas deferens of rats,. The intensity of immunostaining for β- endorphin is not altered by hypophysectomy, and epididymal staining persists after (Castration, β-endorphin, γ-endorphin, and N- and C-terminal ACTH activities are also detected by xadioimmunoassay of male tissue extracts, and their concentrations do not decrease following hypophysectomy. These peptides therefore appear to be of local rather than pituitary origin and may serve a paracrine function within the reproductive tract.