A method is developed for a simultaneous determination of the content of biogenic phenyl- and indolalkylamines and their predecessors. The method includes preparation of a homogenate by cutting the animal tissue and its extraction in acidic butanol, purification of butanol from tissue by centrifugation, subsequent conversion of the substances from the alcohol phase to the aqueous one and lyophilization of the latter. Then thin layer chromatography is performed. For obtaining the neutral separating layer the mixture of the microcyrstalline cellulose JIT and silicagel is used. The mixture ethyl acetate--acetic acid--water (5:1.5:1.5) is used as a solvent. The thin layers of cellulose JIT or ecteolo-cellulose with the solvent 0.01-n HC1 and cellulose JIT with the solvent ethyl acetate--acetic acid-water (5:1.5:1.5) may be used, respectively, for determining the content of the reactions final products, when measuring the enzymic activities of DOPA-decarboxylase and 5-oxytryptophan-decarboxylase.