The water-insoluble poly-beta-cyclodextrin (poly-CM/Nation composite film was easily prepared by casting a Mixed solution of poly-CD and Nation onto substrate plates. FF-IR measurements showed that the 50/50 wt% poly-CD/Nation composite film remained stable on the glass and quartz Substrates after immersion in water for more than 3 h, while it pure poly-CD film was almost completely dissolved by immersion within 1 h. The film stability was also evaluated from the amount of p-nitrophenol (p-NP) inclusion in the film, which was determined from the decrease in UV-vis absorbance of the p-NP Solution into which the film was immersed, The composition dependence of the inclusion amount showed that the film was stable up to 50 wt% CD, but became less stable With further increase in (the CD concentration in the film. From the isotherms for the inclusion of p-NP and 1-naphthoate (1-Naph) into the film, the inclusion (stability) constants were determined to be 3.7 x 10(3) m(-1) and 1.9 x 10(2) M-1, respectively. These results show that the selective inclusion of CD is retained after preparation of the composite film. (c) 2005 Elsevier Inc. All rights reserved.