Naltrexone hydrochloride reportedly produces frequent dysphoria. This has led to speculation regarding the role of endorphins in the etiology of depression. Thirty-six subjects completed an 8-week trial of naltrexone or placebo with frequent mood assessments. No significant differences on POMS scales were noted for either subject group. One subject was discontinued from the study because of a severe dysphoric reaction. Naltrexone does not appear to significantly alter mood over a 2-month time course in nonaddicted, healthy individuals. Subpopulations of patients under physiological or psychological stress may react to naltrexone with dysphoric symptoms.