The chiral host 1 derived from tartaric acid formed the 1:1 inclusion complex with 2 by incorporating one of the enantiomers of 2 into the complex crystal. The irradiation of 2 gave optically pure product 3. The host 1 formed the 2:1 inclusion complex with the prochiral guest 4. The irradiation of this complex gave optically pure 5. In order to elucidate the enantioselective inclusion complexation and the stereospecific control of the photocyclization reaction by host 1, the X-ray crystallographic study of 1 . 2, 1 . 4 and 5 have been undertaken. All structures were solved by direct methods and refined by full-matrix least-squares refinement to give final R values of 0.055 for 1 . 2, 0.040 for 1 . 4 and 0.049 for 5. Each host molecule has one O-H---O intramolecular hydrogen bond and the same conformation. The enantioselective complexation in 1 . 2 will be attained by the specific host-guest interactions observed in the complex crystal, allowing an easy and straightforward method to prepare the optically pure 3 with the determination of the absolute configuration of 3 by reference to the known chirality of 1. The overall structure of the 2:1 inclusion complex of 1 . 4 clearly shows the stereochemical control, which forms the optically pure 5 from the prochiral 4. The absolute configuration of 5 was deduced from the host-guest relative orientation in the 1 . 4 complex crystal and the known absolute configuration of 1.