Recent studies suggest that thrombophilic abnormalities and the use of oral contraceptives (OCs) are the leading causes of cerebral vein thrombosis (CVT). The purpose of this study was to assess the association between CVT and thrombophilic states, OCs, and their interaction. For data sources, we used the MEDLINE, EMBASE, and Cochrane Library databases (January 1994 to March 2005), reference lists of retrieved articles, and contact with content experts. We selected studies comparing the prevalence of OC use and the prevalence of prothrombitic abnormalities in patients with CVT compared with healthy controls. Two reviewers independently selected studies and extracted study characteristics, quality, and outcomes. Odds ratios (ORs) were calculated for each trial and pooled using the Mantel-Haenszel method. Seventeen studies were included. There was an increased risk of CVT in patients using OCs (OR 5.59; 95% confidence interval [CI] 3.95 to 7.91; P < .001), and in patients with factor V Leiden (OR 3.38; 95% CI 2.27 to 5.05; P < .001), with mutation G20 210A of prothrombin (OR 9.27; 95% CI 5.85 to 14.67; P < .001) and with hyperhomocysteinemia (OR 4.07; 95% CI 2.54 to 6.52; P < .001). We concluded that OC users, and patients with factor V Leiden, the prothrombin G20 120A mutation, and hyperhomocysteinemia are at a significantly increased risk of CVT.