In vitro studies of controlled release from chitosan membranes were carried out using drugs of different molecular weight. The release rate was measured in water at 37 degrees +/- 0.5 degrees C by determining the amount of drug released by spect rophotometric analysis. It was found that release of acetamide, nicotinamide, sodium benzoate, sodium salicylate, phenobarbital sodium and sodium cefazoline followed zero-order kinetics. The relation between molecular weight and diffusion coefficient was established.