Eugenol (EU) - PEG adduct was synthesized to improve the chemical and physical properties of eugenol. The phenolic group was covalently bound to the carboxyl group of PEG and the release kinetics were studied in vitro in buffer solution at pH 7.4, in simulated gastric fluid and in mouse plasma. Studies in vitro on the release of the parent drug from the prodrug in various media indicate that the adduct may be sufficiently stable to pass intact into the gastrointestinal tract and release EU into the circulation. The antioxidant activity of PEG-EU adduct was also evaluated. Scavenging activity was absent in the original PEG-EU adduct but gradually increased on the basis of drug delivery.