A convenient synthesis of DL-hydroxy-ornithine is described. Starting from diethyl allylmalonate, it involves treatment with sulphuryl chloride followed by hydrolysis and distillation to give a 90% yield of 2,5-dichloro-4-valerolactone. Condensation of this with two equivalents of potassium phthalimide in dimethyl-formamide gives a quantitative yield of crude 2,5-diphthalimido-4-valerolactone. This lactone is converted quantitatively by acid hydrolysis to DL-γ-hydroxyornithine, isolated as the dihydrochloride of the corresponding 2,5-diamino-4-valerolactone. The over-all yield calculated from allyl chloride is 80%.