Hypercoagulability and thrombotic tendency are frequently induced by a variety of stressors. Clinically, aged subjects and obese patients are more susceptible to thrombotic diseases associated with stress, but the underlying mechanisms are unknown. We investigated the expression of a procoagulant gene, tissue factor (TF), in a mouse model of restraint stress. Twenty hours of restraint stress to mice caused a substantial induction of TF mRNA in several tissues. Importantly, the magnitude of induction of TF mRNA by restraint stress was larger in aged mice compared with young mice. In situ hybridization analysis of the stressed aged mice revealed that strong signals for TF mRNA were localized to renal epithelial cells, smooth muscle cells, adventitial cells, and adipocytes but not to vascular endothelial cells. These observations suggest that restraint stress induces the TF expression in a tissue-specific and cell type-specific manner. Genetically obese mice were also hyperresponsive to restraint stress in the induction of TF gene, especially in their livers and adipose tissues. Stress-induced microthrombi formation was pronounced in renal glomeruli and within the vasculature in adipose tissues of aged mice. Tumor necrosis factor-alpha (TNF-alpha) antigen in plasma was elevated by stress in aged mice and obese mice, and pretreatment of mice with anti-TNF-alpha antibody partially attenuated the stress-mediated induction of TF gene in adipose tissues in these mice. These results suggest that the induction of TF gene may increase the risk of stress-associated thrombosis in older and obese subjects and that TNF-alpha may be involved.