Abstract: A reflector lamp assembly having an integral photo-sensor and sensing circuit arrangement associated therewith provides for sensing the ambient light conditions at a point adjacent the top surface of the lamp envelope. The photo-sensor element is disposed within a sensor housing member mounted along an edge portion of the top surface of the lamp. A channel pathway is integrally formed with the sensor housing member and extends along the side lamp envelope to protect the sensor lead wires extending from the photo-sensor device to the sensing circuitry contained in the threaded screw base. The sensing circuitry is disposed vertically within a cavity formed in the bottom of the screw base so as to achieve optimum thermal dissipation properties for the sensing circuit. A collimator tube can be inserted into an opening formed at the top of the sensor housing member so as to control the field of view for sensing the ambient light conditions occurring near the top surface of the lamp assembly.