Several easy preparative scale (0.5-1.5 g) syntheses of deuterium labelled caffeine, theophylline and theobromine are described. Some new selective syntheses of theophylline and theobromine have been developed. Labelled xanthines are of great interest in qualitative or quantitative isotope dilution-mass spectrometry, coupled with gas or liquid chromatography, currently performed in anti-doping and forensic laboratories.