A series of beta-cyclodextrin complexes containing various guest molecules was studied using computer-aided molecular modeling and conformation analysis techniques. The geometry of each complex was studied using crystallographic data. The positions of the glycosidic O4 atoms indicate that the beta-cyclodextrin molecules are elliptically distorted. This distortion can be related to the van der Waals volume of the guest molecules. This correlation is different for aromatic and non-aromatic guest compounds. Rigid body docking experiments demonstrated that in crystal structures the guest molecule occupies a position in the cavity of nearly minimum interaction energy when there are no other molecules having interactions with the guest molecule. From the crystallographic data several rules could be deduced which seem to determine the conformation of beta-cyclodextrin molecules in complexes. A procedure was developed to construct beta-cyclodextrin molecules that are able to encompass guest molecules having a given van der Waals volume.