Lang NN et al. - Cigarette smoking causes marked impairment of PAR-1–mediated endothelial vasomotor and fibrinolytic function. Relative arterial stasis and near abolition of t-PA release will strongly promote clot propagation and vessel occlusion. These findings suggest a major contribution of impaired endothelial PAR-1 action to the increased atherothrombotic risk of cigarette smokers.