One hundred and thirty-two elderly patients undergoing emergency hip surgery were randomly allocated to receive subarachnoid block (SAB) or general anaesthesia (GA). Using the 125.I fibrinogen uptake test, deep vein thrombosis was found to occur in 17 of 37 patients in the SAB group and 30 of 39 patients in the GA group (P 0.05). Blood loss was 513 ml (+/- SEM 44) in the SAB group and 714 ml (+/- SEM 67) in the GA group (P less than 0.01). Hypoxaemia was present preoperatively (mean PaO2 9.2 kPa). Immediately following general anaesthesia, the mean fall in PaO2 was 0.86 kPa compared with preoperative values but only 0.16 kPa following subarachnoid block (P less than 0.01). At 24 hours postoperatively the fall in PaO2 was similar in both groups and recovered only slowly during the first week. Twelve patients died, three in the SAB group and nine in the GA group. This difference in mortality was not statistically significant.