• Arterial thrombosis most often occurs in medium-sized vessels rendered thrombogenic by atherosclerosis.• Arterial thrombosis usually consists of a platelet- rich clot.• Venous thrombosis is triggered by blood stasis or inappropriate activation of the coagulation cascade.• Venous thrombosis typically involves a clot that is rich in fibrin, with fewer platelets than areobserved with arterial clots.