Aneurysms of the infrapopliteal arteries are rare and they are commonly associated with trauma. We report here on a rare case of a true aneurysm of the posterior tibial artery in a sixty-year-old female. There was no history of trauma, and the serologic tests for the possibility of vasculitis were all negative. The color Doppler ultrasound examination and the multi-detector computed tomographic scan confirmed the diagnosis of a posterior tibial artery aneurysm and these tests revealed no evidence of aneurysms or occlusive lesions in the other arteries. Aneurysmectomy and end-to-end microvascular anastomosis were performed successfully. Preoperative multi- detector computed tomographic scanning is a valuable, noninvasive diagnostic tool to delineate not only the state of the aneurysm, but also that of the distal arterial tree.