Permeation characteristics of NaCl solution were studied using a cellulose acetate reverse osmosis spiral-wound module. The pure water permeability through the module was 0.272L/m²h atm which amounted to 13% of the cell test. The lower permeability of the module is attributed to the permeate flow resistance through the support inserted between the two membrane envelopes. As the pressure was increased, the permeability and salt rejec-tion increased. The permeability and the flux were dependent on the inlet flow rate to the module and the way of pack-ing. For a uniform flow distribution in the module, several distributor tips were designed, among which 30^o cone-type distributor was found to be most suitable.