Four lignan type compounds, lariciresinol, taxiresinol, isolariciresinol and 3-demethyl-iso-lariciresinol, were isolated from the heartwood of Taxus baccata L. (Taxaceae) growing in Turkey through chromatographic techniques. In vivo anti-ulcerogenic potency of these compounds was investigated on ethanol-induced ulcerogenesis model in rats at two different doses, 50 and 100 mg/kg. All compounds were shown to possess significant anti-ulcerogenic activity at both doses. However, the effect of taxiresinol was the most prominent.