Experimental investigation and theoretical study of a different type of two-stage vapor compression cascade refrigeration system using R-134 as the refrigerant are presented. Performance evaluations of two single stage vapor compression systems and two-stage vapor compression refrigeration cascade system are performed with respect to theoretical model developed. In the first section of the experiments, one refrigeration system, namely RU2, is operated. During the experiments, rate of the water flow connecting both systems is kept constant at various values and the voltage across evaporator heaters is increased from 100 to 200 V with intervals of 20 V. In the second part of the first category, experiments are repeated by using different mass flow rates of water. In the second section, two separate refrigeration systems, namely RU1 and RU2 are connected to each other by using the water loop. This system is also called cascade refrigeration system. It is observed that the change in water mass flow rate has little effect on the coefficient of performance for single stage and cascade stage refrigeration systems. It is also observed that the coefficient of performance is mainly a function of evaporator temperature and pressure. When RU2 operating in the single stage refrigeration system is compared with RU2 operating in the two-stage cascade refrigeration system at the same refrigeration load interval (360-460 W), the average percentage values of the decrease in the condensing pressure, the decrease in the compressor power and the increase in the COP are 21.9, 31.7 and 32.7, respectively. (C) 2004 Elsevier Ltd. All rights reserved.