The liquid desiccant air-conditioning system has been identified as a promising technology that has the potential of decoupling and preciously controlling the latent and sensible cooling loads of air-conditioning spaces. The issues of moulds and bacteria growth on the wet surface of chilled water coils of conventional air handling units can be resolved by employing liquid desiccant systems, where moisture is absorbed by antibacterial desiccant solutions instead of condensing at low temperature. Considerable progress has been made by researchers to enhance the dehumidification and cooling performances of liquid desiccant systems, which are coherently presented in this chapter. The thermophysical properties of several liquid desiccants have been evaluated and the opportunities for improving the desired properties by mixing different desiccant materials are explored. Techniques for improving the wettability and flow characteristics of the packing materials are also discussed. In addition, several theoretical models and solution techniques to study heat and mass transfer enhancement opportunities are systematically discussed and compared in this chapter. The potential of a hybrid liquid desiccant system incorporating either a conventional vapour compression system ora vapour absorption chiller is also documented. Finally, some challenges and future research directions are identified and discussed.