After anterolateral thoracotomy, before incision closure, indwelling plastic catheters were inserted percutaneously under digital and/or visual control into the intercostal space of access and the two neighbouring ones. Initially, we injected 25 mg of bupivacaine through each catheter (to a total of 75 mg), and subsequently - on the patients demand - another 15 to 25 mg per catheter. To date, 25 patients received repetitive intercostal nerve blocks by this method (ICB-group). We compared their personal and perioperative data with those of another 30 patients, receiving opiates systemically after major thoracic surgery (SA-group). Multiple blood samples from the ICB-group were analyzed by gaschromatography for bupivacaine concentration-time-profiles. In 19 of 25 patients (76%) the bupivacaine-injections provided sufficient analgesia, 6 patients required additional analgesics. The duration of general anaesthesia (ICB: 174 min vs. SA: 136 min) and the operation time (ICB: 103 min vs. SA: 94 min) were not statistically different in both groups. The periods of intensive care therapy (ICB: 0.7 d vs. SA: 1.2 d), artificial respiration (ICB: 11.2 h vs. SA: 21.6 h) and hospital stay (ICB: 12.1 d vs. SA: 14.2 d) were shorter for the ICB-group. Atelectasis (ICB: 20% vs. SA: 37%) and pneumonia (ICB: 0 vs. SA: 13%) were observed less frequently than in the control group, whereas tachyarrhythmia occurred in 6 of 25 ICB-patients compared to 4 of 30 SA-patients. Nevertheless, none of these parameters reached statistical significance (p less than 0.05). Maximum bupivacaine levels of 0.65 +/- 0.21 micrograms/ml were found after 29 +/- 12 min of intercostal application.(ABSTRACT TRUNCATED AT 250 WORDS)