Oscillographic polarography has been applied for the mescaline and pellotine estimation. These alkaloids produce in 0.5 N NaOH electrolyte a sharp peak within the cathode region of the oscillogram, each of them showing different potential. It makes possible to estimate them at a concentration of 5.10(-6) g/ml. All the forms of Lophophora williamsii were found to contain mescaline and lower content of pellothine, L. jourdaniana--to have equal content of both alkaloide, L. diffusa and L. fricii--to contain pellotine and only traces of mescaline. Plants grown in the greenhouse accumulated the same amount of alkaloids as native plants. Grafting on roodstock which does not produce essential amount of the alkaloids, does not affect the ability of Lophophora to synthesize mescaline and pellotine.