Androsterone sulfate (5alpha-androstan-3alpha-ol-17-one, 3-sodium sulfate) administered to freely moving rats via cerebroventricular cannulae induced analgesia, wet-dog shakes, body jerks, rigidity, Straub tail, hypermotility, excessive grooming, hyperreactivity to stimuli, aggression, escape behavior, EEG spiking, and behavioral and EEG seizures. These responses resemble those produced by certain opiate drugs and by beta-endorphin, an endogenous peptide; they appear during the 5-min infusion period, persist in some cases for several hours, and are diminished by pretreatment with the narcotic antagonist naloxone. These findings indicate that steroid hormones can act upon at least some of the same central pathways influenced by recognized opiate compounds.