nternal iliac artery aneurysms are uncommon, and they are often found only when they have become large with a high attendant risk for rupture and significant resulting mortality. Early detection of these aneurysms is important for appropriate management. Sonography is the screening modality of choice in asymptomatic patients with multiple risk factors. The relatively high incidence of coexisting iliac artery aneurysms with abdominal aortic aneurysms makes sonographic investigation of the iliac artery system essential in the assessment and treatment of high-risk patients. This case demonstrates the appearance of an internal iliac artery aneurysm in a patient difficult to evaluate on physical examination because of large body habitus with acute rupture. The case illustrates how early detection and correlation with CT can aid the diagnosis of iliac artery aneurysm in such an acutely symptomatic patient.