Oil spillage in a body of water has been of great environmental concern. We present in this paper an automatic oil-spill detection system, which employs thin-film and wavefront-splitting interference techniques to determine the existence of surface oil or oil drops in water. Two independent automatic decision-making systems have been built to provide a reliable means of oil-spill detection. Initially a LabVIEWTM computer code and a charge-coupled-device camera were employed to discern and monitor the interference fringes generated from oil slicks. The LabVIEW imaging system was then replaced by a compact and low-cost imaging circuit that functions reliably in a buoy with relatively low power consumption.