SummaryThe frequency of thrombo‐embolic complications as assessed by objective diagnostic techniques was investigated in 262 patients having major pelvic surgery. The lowest incidence of leg vein thrombosis (7 per cent) was found in patients undergoing vaginal hysterectomy. After abdominal hysterectomy for benign pathology the incidence was 13 per cent and after Wertheim's hysterectomy for carcinoma of the cervix 25 per cent. After operation, the highest incidence of leg vein thrombosis (45 per cent) was in patients having surgery for gynaecological carcinoma other than that of the cervix. Fatal pulmonary embolism occurred in two patients (0.7 per cent), one with advanced ovarian carcinoma and the other after surgery for carcinoma of the corpus uteri; non‐fatal pulmonary embolism was diagnosed in six patients (2.2 per cent).