The influence of opiate premedication on analgesic requirements postoperatively was investigated. Out of 98 patients with a lumbar disc prolapse 50 were premedicated with flunitrazepam orally, 48 with pethidine and triflupromazine intramuscularly. The operations were performed under inhalational anaesthesia. The average time up to the first demand for an analgesic was longer following opiate premedication (351 vs. 219 min). Only 45.8% of the patients treated with opiates demanded analgesics postoperatively, compared to 80.0% of those who had a benzodiazepine premedication (P less than 0.01). These clinical data confirm the experimental evidence that pretreatment with opiates diminishes the sustained hyperexcitation of the central nervous system caused by peripheral lesions.