Among the long-term complications that jeopardize bilateral aorto-femoral prostheses, the development of a false aneurysm on the aortic suture line, is indeed one of the most severe. Its frequency, approximately 1 p. cent of cases, is probably underestimated, since its diagnosis, with usual exploration methods, is difficult. The nuclear magnetic resonance (NMR) examination is here particularly indicated and, when in doubt, must be systematically requested, especially in the presence of a false aneurysm of the femoral suture line.