A vapor ejector refrigeration system has been designed and developed to operate with ammonia. In this paper, performance of ejector refrigeration system has been experimentally studied with three different area ratio ejectors by varying operational parameters namely generator, condenser and evaporator temperatures. Effect of non-dimensional parameters like compression ratio, expansion ratio and area ratio on the system performance is studied. Entrainment ratio and coefficient of performance of the system increase with increase in ejector area ratio and expansion ratio and they increase with decrease in compression ratio. © 2006 Elsevier Ltd. All rights reserved.