In continuation of studies on the constituents of Taxus brevifolia Nutt., we investigated fraction FB 10115-H (eluted before taxol during silica column chromatography of a taxol-rich fraction from large-scale bark extraction/purification), which contained two major taxane diterpenes (1 and 3). Compound 1, isomeric with taxol (molecular formula C₄₇H₅₁NO₁₄, confirmed by FAB-MS), was identified as 7-epi-taxol via ¹H-NMR (differences in C-7/C-20 protons analogous to 7-epi-10-deacetyltaxol vs 10-deacetyltaxol); this is the first report of its isolation from T. brevifolia. Heating taxol with azobis(isobutyronitrile) (AIBN) at 80°C in toluene yielded 7-epi-taxol (1) as the only diterpenoid product, confirming its structure. Compound 3, with molecular formula C₄₅H₄₇NO₁₃ (FAB-MS), was identified as a 9,10-diketo taxane (first naturally occurring) via ¹H/¹³C-NMR (two ketone carbonyl absorptions at 207.1 and 188.5 ppm), acetylation (yielding 2'-monoacetate and 2',7-diacetate derivatives), and oxidation of 10-deacetyltaxol with MnO₂. Cytotoxicity in KB cell culture: Compound 1 showed an ED₅₀ of 3×10⁻⁵ µg/ml (slightly less than taxol's 1×10⁻⁵ µg/ml), while compound 3 had an ED₅₀ of 2×10⁻³ µg/ml.