A novel adsorptive process for air separation using a zeolitic adsorbent is described. The process essentially consists of three simple cyclic steps, and it can be used for simultaneous production of an 80-90% oxygen-enriched gas and a 98 + % nitrogen-enriched gas from ambient air. Successful operation of the process requires the use of a zeolite which exhibits high nitrogen adsorption capacity and selectivity from air. The role of nitrogen adsorption selectivity of the zeolite in the vacuum desorption process is examined, and experimental performance data for the air separation process are reported.