Idiopathic cerebral sinus thrombosis (CST) can cause death and serious neurological disability. It is unknown whether smoking, a major risk factor for arterial stroke, is a risk factor also for CST. This work explored the association between smoking and CST in a hospital-based, multicentric, case-control study. In order to avoid the confounding effect of the different risk factors for CST, we analysed the homogeneous subgroup of oral contraceptive users. We compared the prevalence of smoking in a group of 43 young women with CST (cases), whose oral contraceptive use was the only known risk factor, with a sample of 255 healthy contraceptive users of similar age (controls). The prevalence of smoking in cases and controls was similar (26% vs. 29%). The age and geographic area-adjusted odds ratio was 0.9; 95% confidence interval, 0.4-1.8; p=0.7. Smoking in oral contraceptive users does not appear to be associated with CST.