The inclusion complexes (ICs) of unmodified natural and methylated alpha-cyclodextrins (CDs) with biodegradable polymers, polyethylene glycol and poly(epsilon-caprolactone), were prepared by two methods, that is, the one using water and the other using chloroform as the solvent for the respective CDs. The ICs obtained were characterized by IR, WAXD, DSC, and C-13 CP/MAS NMR. It was found that the possibility and the phenomena of IC formation could be varied with the degree of methyl substitution of CD as well as the type of solvents used. Methylated alpha-CDs showed the prominent characteristics of IC formation with polymers in the case where chloroform was used than in the case where water was used as the solvent for CDs, while vice versa in the case of native alpha-CD. (c) 2008 Wiley Periodicals, Inc.