Partially purified rabbit lung N methyltransferase (NMT) was used in an in vitro assay to screen various amines and substrate analogs as potential inhibitors. N Methyltryptamine (NMeT, 10-3M) and 14C S adenosyl L methionine (14C SAM, 2.5 x 10-5M) were used as substrates to form 14C N, N dimethyltryptamine (14C DMT). By thin layer chromatography the product was identified as having the same Rf as authentic DMT. Of 129 compounds studied S adenosyl L homocysteine (SAH) 2 (2 aminoethyl) 5,6 dichlorobenzimidazole dihydrochloride (SKF # 62817 A2), DMT, an equimolar mixture of adenosine plus DL homocysteine, N (2 aminoethyl) pyrrolidine, and 2 (2 aminoethyl) pyridine showed definite inhibitory properties. These constitute potential lead compounds for further research.