Abstract Selectively chain-deuterated fatty acids and phospholipids were synthesized by a modified method of the balloon technique used in the catalytic hydrogenation of unsaturated dicarboxylic acids. The modified method uses a specially designed twin-flask apparatus, with an attached inflatable bulb to control the pressure and act as a safety device. Deuterium gas was generated in situ from sodium borodeuteride and concentrated deuterium chloride in a compartment separate from the reaction mixture of lipid and catalyst. Two catalysts. platinum tetrachloride on activated charcoal and tris(triphenylphosphine)chlororhodium(I) were employed and compared. Quantitative yields of the deuterated products were obtained as analyzed by proton, deuterium. and phosphorus-31 NMR spectroscopy and by mass spectrometry.