The results of studying the pharmacokinetics of aminostigmine, a new reversible cholinesterase inhibitor produced in Russia, are discussed. Tissue radioactivity after intragastric administration of a toxic dose of aminostigmine was quite quickly absorbed from the intestinal lumen. The half-life period of aminostigmine exceeded considerably that of earlier studied carbamates and correlated with the clinical manifestations of the drug effects. This confirms that the use of aminostigmine in the treatment of neurologic and somatic diseases is preferable.