The hypothesis for this therapeutic use of delta sleep-inducing peptide (DSIP) was based on several animal studies conducted by Tissot. He showed that morphine, alcohol, pentobarbital as well as DSIP, when injected directly into the bulbo-mesencephalo-thalamic recruiting system, induced slow-wave sleep with numerous spindles. In all cases, this effect was reversed by Naloxone. Thus, it has been postulated that DSIP possesses an agonistic activity on opiate receptors and might be of value in the treatment of withdrawal syndromes. Therefore, DSIP was administered intravenously to 107 inpatients presenting with symptoms of alcohol (n = 47) or opiate (n = 60) withdrawal. The assessment of effect was based on the clinical evaluation by the physician and the nursing staff. Approximately 13% of the patients from the first and 22% from the second group did not fulfil the requirements for the evaluation of treatment. In, respectively, 97 and 87% of opiate and alcohol addicts, the clinical symptoms and signs disappeared after DSIP administration or improved markedly and rapidly. Anxiety, however, was slower to decrease. On the average, the clinical symptomatology had a more prolonged course and a higher number of DSIP injections were required for opiate addicts than for alcoholics. Tolerance to the DSIP treatment was good, aside from headaches reported by a few patients.