Background and Purpose— Pregnancy and the postpartum period are generally considered to be risk factors for cerebral venous thrombosis (CVT), but no controlled studies have quantified the risk. Methods— Case-control study using data of consecutive adult patients with CVT from 5 academic hospitals and controls from the Dutch MEGA study (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis). Men, women over the age of 50, women using oral contraceptives or with a recent abortion or miscarriage were excluded. We adjusted for age and history of cancer, and stratified for pregnancy versus postpartum, and 0 to 6 versus 7 to 12 weeks postpartum. Results— In total 163/813 cases and 1230/6296 controls were included. Cases were younger (median 38 versus 41 years) and more often had a history of cancer (14% versus 4%) than controls. In total 41/163 (25%) cases and 82/1230 (7%) controls were pregnant or postpartum (adjusted odds ratio, 3.8; 95% CI, 2.4–6.0). The association was fully attributable to an increased risk of CVT during the postpartum period (adjusted odds ratio, 10.6; 95% CI, 5.6–20.0). We found no association between pregnancy and CVT (adjusted odds ratio, 1.2; 95% CI, 0.6–2.3). The risk was highest during the first 6 weeks postpartum (adjusted odds ratio, 18.7; 95% CI, 8.3–41.9). Conclusions— Women who have recently delivered are at increased risk of developing CVT, while there does not seem to be an increased risk of CVT during pregnancy.