The complexation of esters, amides, carboxylic acids, and inorganic ions with alpha-cyclodextrin (α-CD) in aqueous medium was studied by calorimetry. Thermodynamic parameters for the formation of the host–guest complex have been determined. All these processes seem to be enthalpy driven. The entire ester molecule probably penetrates the α-CD cavity. The carboxylic acids hydrogen bond to the α-CD while the alkyl part of the acid enters the cavity. Amides undergo only a weak interaction with the host molecule α-CD. Larger anions interact more strongly with α-CD than do smaller anions; this may be, in part, due to the relative ease of desolvation of the larger anion. The cation seems to play some role in the complexation process with α-CD.