We examined naloxone-precipitated withdrawal as a meansfor rapid opiate detoxification and induction onto naltrexone, In 29 patients dependent on methadone (5 to 20 mg/day), abstinence was precipitated by an injection qf naloxone. Repeated injections of naloxone were given subsequently until symptoms of abstinence were no longer induced. Successive injections induced less intense withdrawal assessed by vital signs and ratings on abstinence scales. The most rapid procedure consisted of 1.2 mg naloxone every 30 min for 3 to 6 hr, followed by hourly increasing doses of naltrexone. This procedure allowed transition from opiate dependence to naltrexone maintenance (50 to 100 mg/day) within 48 hr. The results are consistent with assumptions that antagonists actively displace opiates from receptor sites.