Tissues from two juvenile brown bears (Ursus arctos), suspected to have died from yew (Taxus baccata) toxicosis, were chemically examined using thin layer chromatography and high performance liquid chromatography. Extraction and analysis were conducted on heart and liver tissue samples as well as stomach content from the two bears and also on fresh material from an authenticated yew tree which was used as a standard for comparison. The taxine complex comprised of taxine B, 1-deoxytaxine B, isotaxine B, 2-acetyltaxin B, 1-deoxyisotaxine B, 2-acetylisotaxine B, and cinnamates were detected in all extracted samples. taxine B and its isomer isotaxine B are the main toxic constituents in yew. The heart, the target organ of taxine B, is arrested when reaching the lethal tissue concentration of taxine complex. In the present cases, the concentration in the hearts was found to be 37 and 17 μg taxine complex per gram tissue, respectively. As no further absorption into the heart occurs following cardiac arrest, the concentration determined is the actual lethal tissue concentration. Yew ingestion was confirmed by microscopic examination of stomach contents of both bears.Histopathological findings of contraction band necrosis in heart specimens were also consistent with yew intoxication.