Background. Early detection of asymptomatic abdominal aortic aneurysms (AAAs) has been advocated to decrease the high mortality rate of ruptured AAAs. The purpose of this study was to document how AAAs were detected, whether AAAs not detected on physical examination (PE) were palpable, and what factors precluded detection by PE. Methods. Two hundred forty-three patients undergoing elective infrarenal AAA repair at a Veterans Affairs, county, or university hospital during a 10-year period were analyzed retrospectively. The method of initial detection of the AAA, size of the AAA at initial detection and before repair, and whether the AAA was palpable on preoperative PE were recorded, and the body mass index [BMI; weight in kg/(height in meters)2] was calculated. Obese patients were defined with MBI of greater than 85th percentile. Results. Only 93 (38%) patients had their AAAs initially detected by PE; the remainder (62%) were found incidentally on radiologic examinations performed for other indications. Patients with p<0.001), but there was no difference in AAA size (PE, 5.8±1.6 cm; incidental, 5.5±1.9 cm, not significant). Forty-three percent of patients with AAAs detected on radiologic examination had palpable AAAs and should have been detected on PE. Overall, 55 (23%) AAAs were not palpable on preoperative PE, even when the diagnosis was known. Obese patients had only 15% of AAAs detected by PE, and only 33% were palpable. Conclusions. AAAs are underdiagnosed by PE, especially in obese persons. More widespread abdominal examination to detect a widened aortic pulse would improve detection of AAAs.