The study of host-guest interactions has recently expanded from solution chemistry to the gas phase, where solvent effects are not present, allowing better understanding of the intrinsic phenomena responsible for molecular recognition. Important aspects under investigation include the mechanism of interaction, the identification of binding groups, as well as the discovery of structural requirements for the host to undergo inclusion complexation. The information gained from these gas phase studies can be exploited to design new practical applications of host-guest chemistry, particularly when gas-solid interactions are involved. Analytical devices such as gas sensors and chromatographic adsorbing cartridges take advantage of the structural recognition capability of the host to achieve high levels of selectivity.