The fatty portion of the hexane extract from roots of Trigonia fasciculata has been determined by GC/MS analysis of the methyl ester mixture. Seventeen fatty acids were identified and oleic acid (38.8%) was the major component. The GC/MS analysis of the less polar fraction of the non-saponifiable part of the root hexane extract allowed the identification of fifteen sesquiterpenes and alpha-santalene (28.4%) was the major component. Chromatography over silica gel of the more polar fraction allowed the isolation of two known compounds: betulinic acid and friedelin, and a novel diterpene 7-(2-hydroxy-acetyl)-10-hydroxy-tetradecahydro-1-methylene-4b,7,10a-trimethyl -phenantrene (6alpha-hydroxy-15-oxo-allodevadarool), all unknown for the species. Structure determination was accomplished by chemical derivatization, comparison to literature data and spectral analysis, including 2D NMR (COSY, HETCOR, COLOC) and X-ray crystallography