The addition of a plane reflector to a box-type solar cooker increases the obtained cooker temperature and this depends upon the efficient orientation of the cooker. In order to find out the effect of the cooker orientation on its performance, the present analysis is carried out. A method in outlined to find out a reflector performance factor and an orientation factor that depend upon the elevation angle of the sun, the solar surface azimuth angle and the reflector tilt angle. The analysis is applied to a cooker placed at Aden (Yemen). The results indicate that with proper cooker orientation the improvement in the performance of the cooker due to the reflector reached during winter is more than 100% at lower elevation angles and is more than 60% at higher elevation angles. It is concluded that with the help of the analysis the optimum position for any place, for any day of the year and for any specific time of the day can be found. (C) 2001 Elsevier Science Ltd. All rights reserved.