A single basin solar still (SBSS) is designed and constructed. A simple transient mathematical model is presented for the still. It is based on analytical solution of the energy-balance equations for different parts of the still. Analytical expressions for temperatures of different components have been obtained. The thermal performance of the still has been investigated both experimentally and theoretically. Good agreement between experimental and theoretical results is observed. The influence of cover slope on the daily productivity of the still was investigated. Effect of heat capacity of basin water on the daylight and overnight productivities was also studied. It is inferred that, the productivity of the still decreases with an increase of heat capacity of basin water during daylight and the reverse is the case overnight. The optimum tilt angles of the still cover were found to be 10 and 50 degrees during the summer and winter seasons, respectively, in Tanta (30 degrees 47＇N). The daily efficiency of the still is about 27%.