An X-band microwave life-detection system has been developed for detecting the heartbeat and breathing of human subjects lying on the ground at a distance of about 30 m or located behind a cinder block wall. The basic principle of the system is to illuminate the subject with a low-intensity microwave beam, and then from the back-scattered microwave signal, extract the heart and breathing signals that modulate it. The circuit description of the system and some experimental results are presented. Potential applications of the system are noted.