The hydroxyl group (-OH) is the exclusive functional group of poly(vinyl alcohol) (PVA), and there must be abundant hydroxyl groups on its surface. This study determined the superficial hydroxyl group amount of PVA (degree of polymerization = 1700 +/- 50, degree of alcoholysis >= 99.0%) by a chemical method (titration) and an instrumental method [X-ray photoelectron spectroscopy (XPS)]. The results showed the following: (1) the order of magnitude of its superficial hydroxyl group amount was about 3.8 x 10(-5) mol/cm(2) by the acylation method with a single functional group reagent (acetic anhydride); (2) the hydroxyl group amount outcome by the esterification method with a bifunctional group reagent (toluene-2,4-diisocyanate) was much lower than that by the acylation method (ca. 7.74 x 10(-7) mol/cm(2)); and (3) the relative content of oxygen on the PVA surface given by XPS surface analysis was 22% of the total, which was lower than that of the theoretical amount (36%). On the basis of the results, it was shown that the number of available or free hydroxyl groups was less than theoretical amounts. Although there was a difference among the outcomes, it could be useful for providing a quantitative reference when the hydroxyl group on a solid PVA surface is used for surface modification; moreover, the outcomes and differences also offer us knowledge of the surface modification efficiency. (c) 2008 Wiley Periodicals, Inc.