By employing an irreversible thermodynamic approach the optimum performance of an cascaded absorption heat-transformer system is investigated. To get closer to real machines, the effects of thermal resistances and internal irreversibilities on the performance of the cascaded cycle is considered. An improved equation for the coefficient of performance (COP) of the system under consideration was obtained. The analyses show that the cascaded cycle has a significant increase in the systems gross temperature lift (GTL) over the single stage heat-transformer. (C) 2002 Elsevier Science Ltd. All rights reserved.