Air conditioning is essential for maintaining thermal comfort in indoor environments, particularly for buildings located in the tropics where the weather is both hot and humid. Today, air conditioning, comprising cooling and dehumidification, has become a necessity in commercial and residential buildings and even in many industrial processes. In tropical climates, the energy consumed due to heating, ventilation and air-conditioning (HVAC) alone can exceed 50% of the total energy consumption of a building. This significant figure is primarily due to the heavy-duty placed on cooling systems to remove both sensible and latent heat loads. Therefore, there is tremendous potential to improve the overall efficiency of air-conditioning systems for building applications. One of the simplest and neatest ways to reduce energy consumption for air conditioning is to decouple the sensible and latent loads imposed on cooling systems. When a separate technology is solely able to dehumidify the supply air, the cooling load imposed on the cooling system can be markedly reduced. Accordingly, the energy efficiency for cooling is promoted. This review chapter provides a key update on recent developments in air-conditioning systems, particularly innovative technologies in cooling and dehumidification. Key technologies related to sustainable cooling include absorption/adsorption cooling and dew-point evaporative cooling. Technologies connected with dehumidification involve new generations of solid-based desiccant dehumidifiers, liquid-based desiccants and novel membranes that are able to sieve out water vapour when a transmembrane pressure is provided.