The present study was aimed to develop controlled porosity osmotic pump (CPOP) tablets of ritonavir, a protease inhibitor for the treatment of acquired immune deficiency syndrome (AIDS).Ritonavir tablets were prepared by wet granulation method using controlled release polymer hydroxypropyl methylcellulose (HPMCE5LV) with different concentrations of osmogen sodium chloride. The core tablets were coated with cellulose acetate (CA) as a wall forming material, polyethylene glycols as a flux regulating agent, and sorbitol as a pore forming material in semipermeable membrane (SPM). The formulated tablets were evaluated by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), micromeritic properties, post compression parameters, in vitro drug release (IVDR), and scanning electron microscopy (SEM). Among developed formulations RS5 batch showed 97.24  0.42% drug release at 14 h. Zero order, first order, Higuchi, Korsmeyer-Peppas, and Hixson-Crowell models were used to assess the in vitro release kinetics of different batches as well as the mechanism of drug release. The results of optimized formulation was found to exhibit zero order kinetics independent of the pH and agitation intensity, but depended on the osmotic pressure of dissolution media. This indicated that mechanism of drug release was due to osmotic pressure. Results of SEM study showed the formation of pores in SPM from where the drug release occurred. Short term stability study at 40 ± 2ºC/75 ± 5% RH for three months was carried out for the optimized batch. The results from stability study indicated that there was no significant change in weight variation, % friability, drug content, and in vitro drug release. The present study confirmed that increasing the concentration of osmogen, the drug release from the system also increased, and the system could provide controlled release of the drug.