Material isolated from Onobrychis viciifolia Scop. (sainfoin) was fully characterized as δ-acetyl-L-ornithine. Previous reports regarding this compound did not adequately characterize either the position of acetylation or the optical isomer of ornithine involved. Procedures for discriminating between the chromatographically-similar δ-acetylornithine, α-acetylornithine and γ-amido-α-aminobutyric acid (γ-acetyldiaminobutyric acid) are described. A survey of leguminous seed suggested (a) that acetylornithine was not confined to a particular taxonomic group and (b) the occurrence of acetyldiaminobutyric acid in the Leguminosae.