The safety and value of naloxone as a therapeutic aid was demonstrated in a large population of narcotic dependent persons over a two-year period. Naloxone was used to precipitate the narcotic withdrawal syndrome. This withdrawal syndrome was rated according to a previously developed scale. Retrospectively, naloxone rating scores were correlated with the patients' initial dose of methadone. With patients who received 0.8 mg naloxone, good correlation was obtained between the naloxone test score and the optimum methadone dose (mg), as indicated by the patients' physical status during the initial three days of methadone treatment. Three hundred and sixty-three tests were administered to 343 persons and no individuals developed any serious effects such as convulsions, syncope or cardiovascular collapse.