The sterol and fatty acid compositions of Epifagus virginiana, which is a nonphotosynthetic flowering plant, have been examined by combined gas liquid chromatography-mass spectrometry (GLC-MS) and nuclear magnetic resonance (NMR). The organism exhibited a typical higher plant Δ5-sterol profile with the C-24 alkyl group oriented "α" for the major sterol Trace amounts of 24-methylenecycloartanol and cycloeucalenol established connection with the first cyclic intermediate (cycloartenol) in photosynthetic plant sterol biosynthesis. In a separate in vitro experiment, excised root and stem tissue were incubated with two labeled triterpenoid precursors, [2-3H] lanosterol and [2-3H]cycloartenol. Both the radioactive compounds were converted to labeled [3H]sitosterol indicating the presence of an active biosynthetic pathway in Epifagus. Characteristic photosynthetic higher plant fatty acids were also present, and the polyenic acid was identified as α-linolenic acid.