Continuous intrapleural bupivacaine administration was assessed in a randomized double-blind manner with respect to its analgesic effect and its impact on breathing after thoracotomy. The pleural cavity was infused continuously for 48 hours in 24 patients following thoracotomy for pulmonary resection. 12 patients received 10 ml/h of bupivacaine hydrochloride 0.5% solution, and 12 patients 10 ml/h NaCl 0.9% solution. There were no differences in the patients' characteristics, extent of surgery, mode and duration of general anaesthesia. There were no complications related either to the catheter or to bupivacaine. The amount of postoperative opioid, given on request, was used to assess the effect of bupivacaine administration on pain relief. Post-thoracotomy breathing was assessed by measuring the forced vital capacity (VC) prior to and after physiotherapy. The VC values measured 24 h, 36 h and 48 h after the operation were similar in both groups of patients with or without bupivacaine administration (p greater than 0.05). Patients given bupivacaine required significantly less opioid analgesia than those who received NaCl 0.9% at 24 h (p less than 0.001), 36 h (p less than 0.001) and 48 h (p less than 0.01) after the operation. Continuous intrapleural bupivacaine analgesia through a paravertebral catheter positioned in the paravertebral groove is safe and provides efficient pain relief after thoracotomy.