A cylindrical shaped box type solar cooker was constructed and its thermal performance was tested under the prevailing weather conditions in Karabuk, Turkey. Experiments were conducted on a single glazed cooker with a plane reflector and one cooking pot during August 2004. The international test procedure was applied to the solar cooker and the stagnation temperature, and the sensible water heating tests were performed to predict the heating characteristic curves. The results obtained from the tests were used to calculate the two figures of merit, overall thermal efficiency, specific and characteristic boiling times as well as the cooking power. The first figure of merit obtained was greater than value suggested in the international standard test procedure. The second figure of merit was found to increase almost linearly with the quantity of water. These figures of merit are then used to predict the characteristic heating curves. Good agreement exists between the predicted heating curves and the experimental results. The solar cooker with 1 m(2) aperture area is able to boil 1 kg water in 13.6 min with 30.5% daily thermal efficiency.