A numerical study was carried out to investigate the transient thermal performance of a new humidification-dehumidification solar still. The still body is a relatively thin rectangular box with a top glass cover and bottom condensing sheet. The still body is divided (by a central insulated stepped sheet carrying a group of basins) into two chambers: the upper evaporation chamber and lower condensation chamber. Air is circulated between the upper evaporation chamber (where it is heated and humidified) and the lower condensation chamber (where it is cooled and dehumidified for water production). The influence of different environmental, design, and operational parameters on the still productivity was investigated. The results indicated that increasing the solar intensity, ambient temperature, basin absorbitivity, and initial saline water temperature increases the system productivity. On the other hand, increasing wind velocity, basin insulation thickness, evaporation and condensation surface areas, condenser emissivity, and saline water mass has little effect on productivity. The interesting result is that the decreasing airflow rate has insignificant influence on system productivity. Decreasing airflow rate from 0.1 to 0.001 kg/s partially increases the productivity from 5.2 to 5.3 L/m(2). The physical explanation and implications of these findings are explained.