Deep venous thrombosis (DVT) and pulmonary embolism (PE) cause significant morbidity and mortality in orthopaedic surgical practice, although the incidence following surgery to the lumbosacral spine is less than following lower limb surgery. Our objective was to compare our rate of thromboembolic complications with those published elsewhere and investigate whether the adoption of additional pharmacological measures reduced the incidence of clinically evident DVT and PE. This retrospective study was undertaken to investigate the incidence of DVT/PE during the 10 years from 1 January 1985 to 31 December 1994, and then to assess the effectiveness of an anticoagulant policy introduced during 1995 using low dose aspirin or LMH in high risk cases. All records for spinal operations were reviewed for thrombo-embolic complications by reference to the Scottish Morbidity Record form SMR1. To ensure that all patients were compliant with the policy, data for the whole of 1995 was omitted and the period 1 January 1996 to 31 December 2003 was taken to assess its effectiveness. Surgery was done with the patient in the kneeling, seated prone position which leaves the abdomen free and avoids venous kinking in the legs. Records of a total of 1,111 lumbar spine operations were performed from 1 January 1985 to 31 December 2004 were reviewed. The overall incidence of thrombo-embolic complications was 0.29%. A total of 697 operations were performed from 1 January 1985 to 31 December 1994 with two cases of DVT and no cases of PE giving thromboembolic complication rate of 0.29%. During the period 1 January 1996 to 31 December 2003, 414 operations resulted in one case of DVT and no cases of PE, a rate of 0.24%. The incidence of symptomatic thrombo-embolic complications in lumbar spinal surgery is low in the kneeling, seated prone operating position, whether or not anticoagulation is used.