Abstract The synthesis of deuterium labeled tryptamine derivatives,[2-(1H-indol-3-yl)-[2 H 4]- ethyl]-dimethylamine (DMT),[2 H 10]-diethyl-[2-(1H-indol-3-yl)-ethyl]-amine (DET),[2-(1H- indol-3-yl)-ethyl]-[2 H 6]-dipropyl-amine (DPT) and [2 H 2]-alpha-methyltryptamine (AMT) is described. The isotopically labeled compounds are used as internal standards in gas chromatography-mass spectrometry (GC-MS) assays.