A series of poly(vinylalcohol-co-ethylene-graft-acetylsalicylic acid) hydrogel (Hi) of different acetylsalicylic acid (AcSa) contents were prepared by grafting of AcSa groups to poly(vinylalcohol-co-ethylene) in an esterification reaction and then crosslinking with oxalic acid. The Hi was characterized by the solubility test, DSC, NMR, and SEM analyses. The AcSa released by retroesterification of Hi at 37 degrees C and at different pHs during 92 h. The results revealed that the amount of AcSa released from Hi depended on the initial content of AcSa in Hi and the pH of the media. In general, the results revealed that the PEVA-graft-AcSa (H2), which contained initially 1.59 mg of AcSa, released at pH 1 a lower amount of AcSa (0.08 +/- 0.02 wt % of AcSa/h), stable during the longest period (85 h). On the reverse H3 which contained 2.05 mg of AcSa presented a highly efficient release rate at pH 7. This hydrogel was able to release 0.80 +/- 0.05 wt % of AcSa/h, stable for about 60 h. From the first view, this finding seemed to be very important in the drug-release domain, because the hydrogel prepared in this work was able to release a greatest amount of aspirin directly into the intestines (neutral pH). (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013