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Cyclodextrins (CDs) are known to form inclusion complexes with various kinds of substances, which are included into the CD’s hydrophobic structural cavities without any covalent bonding. It is well known that the presence of water is essential to the formation of the inclusion complex. The inclusion complex cannot be formed by the simple mixing of the CD’s in dry powder form with the aromatic compounds such as d-limonene. Recently, we have studied the formation of the inclusion complex by kneading a slurry mixture of jS-CD and d-limonene at low moisture, and found that the formation of the inclusion complex was influenced by initial moisture content [1]. Saenger et al [2] speculated that the release of the included water molecules in the CD’s cavity, called “high energy water”, was the major driving force of the inclusion. However, there has been no systematic research dealing with the effect of moisture content on the amount of inclusion complex. From a practical point of view in the pharmaceutical use of cyclodextrins, it is important to examine the effect of the presence of other organic solvents such as ethanol in aqueous solutions of CDs [3]. In this study, we focus our attention on the influence of water and ethanol contents on the formation of the inclusion complex at lower water contents. The minimum number of water molecules required for including d-limonene into a-, p- and y-CD’s cavity were measured by the micro-aqueous method.