: Postmenopausal hormone therapy increases the risk of venous thrombosis. Sex hormone binding globulin (SHBG) is a suggested marker of 'total estrogenicity'. The study objective was to evaluate the impact of hormone therapy on SHBG and the association with coagulation variables. The study populations comprised 202 healthy postmenopausal women randomized to treatment with low-dose or conventional-dose hormone therapy, tibolone or raloxifene (RET-study) and 140 women with a history of venous thrombosis randomized to conventional-dose hormone therapy or placebo (EVTET-study). SHBG was determined in serum collected at baseline and after 12 weeks. In healthy women, conventional-dose hormone therapy increased SHBG with mean 9.7 (95% confidence interval 4.8-14.5) nmol/l, low-dose hormone therapy by mean 5.9 (0.4-11.5) nmol/l, raloxifene by mean 7.2 (3.9-10.4) nmol/l, while tibolone reduced SHBG with mean -25.1 (-29.9 to -20.4) nmol/l. SHBG correlated with protein S, tissue factor pathway inhibitor (TFPI) and protein C at baseline, and with protein S and TFPI after 12 weeks, but the change in SHBG from baseline to 12 weeks was only associated with the change in activated protein C (APC) resistance. In women with a history of venous thrombosis, the mean increase in SHBG was 13.6 (8.4-18.9) nmol/l in the conventional-dose hormone therapy group, with no change in the placebo group. Baseline SHBG was higher among women who developed recurrent venous thrombosis on conventional-dose hormone therapy. SHBG correlated with several coagulation inhibitors, but the change in SHBG induced by postmenopausal hormone therapy was only associated with the change in APC resistance.