Glycolaldehyde, glycollate and glyoxylate, but not formate or glycine, decrease the amount of acetoacetate formed by rat-liver slices.Incubation of glyoxylate and acetoacetate in neutral solution at 370 results in a stoicheiometric removal of the two acids and the reaction is accelerated by Mg2+ ions.A product of this condensation reaction has been isolated and characterized as f-acetylacrylic acid (4-oxopent-2-enoic acid).It is suggested that the apparent antiketogenic action of glyoxylate (and also of glycolaldehyde and glycollate) is due to its non-enzymic condensation with acetoacetate.The occurrence of y-hydroxyarginine in plants has been confirmed by the isolation of its lactone from seeds of Vicia sativa.A new natural amino acid, y-hydroxyornithine, has been identified by chromatography and ionophoresis in the seeds of Vicia onobrychoide8 and V. unijuga.The closely related genera, LathyruB and Vicia, characteristically store different groups of guanidino amino acids.A colour reaction for the identification of y-hydroxyornithine on paper is described.A study of the free amino acids and related compounds in the seeds of 49 species of Lathyru8 (Bell, 1962a) revealed.the presence in the seeds of L. aphaca, L. cyan?s, L. 8phaericus and L. tingitanuw of lathyrine (i.e. 2-aminopyrimidin-4-ylalanine; Bell & Foster, 1962), homoarginine (Bell, 1962b)and a third new amino acid designated B3, subsequently reported to bo y-hydroxyhomoarginine (i.e. o-amino-E-guanidino-y-hydroxyhexanoic acid; Bell, 1963). The existence of the last-named amino acid had been predicted by Rao, Ramachandran & Adiga (1963), who visualized it as a likely inter-