Two cases of massive iliopsoas muscle bleeding leading to fatal exsanguination are presented. Both patients (two women, 61 and 74 years old, respectively) received oral anticoagulation with phenprocoumon. The intramuscular bleeding occurred spontaneously in women of relatively good physical condition. Intriguingly, phenprocoumon concentrations were within the therapeutic range (1.55 &mgr;g/ml and 1.26 &mgr;g/ml, respectively) as detected by toxicologic analysis. These cases demonstrate that severe bleeding in the iliopsoas muscle has to be considered in all patients receiving anticoagulant medication, even in those who have coagulation parameters within the therapeutic range. Especially in older patients with a high degree of comorbidity or in patients receiving analgesic drugs, the potential of fatal outcome of iliopsoas muscle bleeding seems to be of clinicopathologic relevance.