In this paper, a new method for exergy analysis of humidification-dehumidification (HD) desalination systems is presented. It is based on the principle that there are exergy losses wherever the driving forces exist. A methodology was developed for investigating various parametric effects on exergy losses. The method involved developing a sink and source model as well as basic relations in the system. Results showed that the mass transfer phenomenon does not have any effect on the total exergy losses of the HD systems. Heater was the largest irreversibility resource. Flow rate of the Un-heated fluid and the maximum temperature of the system had key roles in the total exergy losses. An optimum point for the water-heated HD desalination system is also introduced. Finally, some comparisons are proposed between the water-heated and the air-heated HD desalination systems. (C) 2011 Elsevier B.V. All rights reserved.