The structural specificity and the chemical dynamics between β-cyclodextrin and aspirin were studied by FT-IR, UV, ¹H NMR, ^(13)C NMR, and FAB-MS spectroscopy in solution and solid state. A stable solid inclusion complex was prepared by the recrystallization method. From the spectral changes of the host and guest molecules, orientational preference for binding in the cyclodextrin cavity was determined.