The frequency of local venous reactions after the injection i.v. of etomidate or thiopentone was studied in 61 patients undergoing surgery for prolapsed lumbar disc. Of the patients who received etomidate, 24% developed thrombophlebitis in the period after operation (up to 14 days). Of the patients who received thiopentone, 4% developed thrombophlebitis in the period after operation. Pain on injection occurred in 24% of the patients receiving etomidate, but there was no correlation between pain on injection and the subsequent thrombophlebitis.