62 but not all, 8 63 studies. We acknowledge potential limitations. Firstly, our findings are limited to the studies included in this meta-analysis. Although this may imply a study selection bias, we pre-specified the study selection criteria, thus minimising such bias. The advantage gained with a patient level meta-analysis was in having a large sample of original data and the ability to adjust for potential confounders. 11 Secondly, unmeasured determinants may explain the differential risk of recurrence of venous thromboembolism in men and women, and additional research is needed to explain our findings. Thirdly, including patients with hormonal therapy associated initial venous thromboembolism as unprovoked disease may be questioned. We made this decision a priori, and the fact that hormonal therapy is considered to be a weak risk factor for venous thromboembolism compared with major risk factors such as surgery justifies this. 16 Furthermore, a standard definition of unprovoked venous thromboembolism is lacking; some studies have included hormone associated venous thromboembolism as unprovoked, 4 26 63 64 whereas others have not. 36 65 None the less, we pre-specified analyses that would adjust for these subgroups of patients when assessing risk of recurrence in men and women. Finally, our findings are based on a predominantly white population and may not be applicable to other racial groups, in whom further research is needed to assess prognosis of venous thromboembolism. 66 Implications of findings Our findings suggest that in patients with a first unprovoked venous thromboembolism, patient's sex may be an important consideration