Suloctidil (200 mg t.i.d.) was compared with placebo in a randomized, double-blind trial to assess its value in preventing deep venous thrombosis (DVT) in high-risk neurosurgical patients, comprising 136 patients with brain or spinal tumour, head or spinal injury, or subarachnoid or intracranial hemorrhage. I fibrinogen leg scanning and impedance plethysmography were performed for up to 14 days to detect DVT. The two groups were also evenly balanced for DVT risk factors. Seventeen of 68 patients (25%) (95% confidence interval, 15–35%) treated with suloctidil and 12 of 68 patients (21%) (95% confidence interval, 11–32%) treated with placebo developed deep venous thrombosis. This observed difference in outcomes is not statistically significant (X = 1.096; p=0.30). The estimated 95% confidence interval for the true difference in the incidence of DVT between suloctidil-treated and placebo-treated patients ranges from an 11% benefit in favour of suloctidil to an 18% benefit in favour of placebo. Major deep vein thrombosis occurred in two patients on suloctidil and three patients in the placebo group; there were no fatal pulmonary emboli during the 14-day study period, during which time four patients in each group died of non-thromboembolic complications. There was no observed difference in hemorrhagic complications. Long-term outcomes at three-months follow-up were similar between the two treatment groups. It is concluded that there is no real evidence that suloctidil (200 mg t.i.d.) is an effective regimen for the prevention of DVT in high-risk neurosurgical patients.