Findings consistent with the hypothesis that increased central opioidergic tone contributes to the pruritus of cholestasis provide a rationale for treating this form of pruritus with opiate antagonists. However, initiation of therapy with an opiate antagonist in a cholestatic patient may precipitate a transient opioid withdrawal-like reaction. A woman with chronic cholestasis and disabling pruritus experienced severe transient opioid withdrawal-like reactions after oral administration of 12.5 and 2 mg naltrexone. Subsequently, naloxone was administered by intravenous infusion. Initially, the infusion rate was low and subtherapeutic. It was gradually increased to a rate known to be effective in inducing opioid antagonism. Oral naltrexone was then reintroduced without any reaction occurring. During the ensuing 12 months, while taking naltrexone, 25 mg daily, the patient has been completely free from pruritus. These observations strongly support the hypothesis that increased central opioidergic tone is a component of the pathophysiology of cholestasis.