Abstract: A portal access control system is disclosed for preventing unauthorized entry from a public area into a secure area. The system utilizes input from several different sensors, including: passive IR sensors, motion detectors, photo detectors and authentication devices. Also, the passage time of an individual through the open portal may be determined. Based on selected combinations of one or more sensor inputs, the portal access control system can detect passage into the secure area by a lone perpetrator and also by tailgating behind an authorized user.