Sweeping gas membrane distillation was investigated as a possible technique for desalination by using a shell-and-tube polypropylene membrane module. Humid air was employed as the vapor carrier gas and the feed solution was circulated in counter-current through the lumen side of the membrane module. The effects of the process parameters, liquid feed flow rate, feed temperature, air flow rate and salt concentration on the distillate flux have been investigated. A theoretical model that considers the heat and mass transfer through microporous and hydrophobic membranes as well as the temperature and concentration polarization effects was developed and validated with the experimental data of distilled water and sat aqueous feed solutions. The distillate flux decreases with the salt concentration, but no drastic flux decline was observed with the increase of the feed electrical conductivity up to 182 mS/cm. High-purity water was obtained.