The cycles of metal-hydride heat-pumps have three operating modes-heat upgrading, heat amplifying, and refrigeration. Carnot analyses of these cycles show that in the case of the heat-upgrading mode a prerequisite of high efficiency is that the reaction enthalpy for the high-pressure hydride must be lower than that for the low-pressure hydride (ie Delta H-H < Delta H-L). In the case of the heat-amplifying and refrigerating modes the reaction enthalpy for the high-pressure hydride must be greater than, or equal to, that for the low-pressure hydride (ie Delta H-H greater than or equal to Delta H-L). The coefficient of performance (COP) has been shown to be inadequate by itself for evaluation of a metal-hydride heat-pump cycle; therefore three evaluation criteria are put forward for a comprehensive assessment-namely actual COP, alloy output and temperature output. In the present study the effects of some parameters on these criteria are discussed. Relative to other conventional cycles, the COP values of metal-hydride heat-pumps are low, and further research is needed to improve their performance.