The affinities of some cholinomimetics (acetylcholine, methacholine, carbachol, oxotremorine, aceclidine and pilocarpine) for muscarinic acetylcholine receptors of various isolated tissues (rat spontaneously beating atria, rat electrically stimulated left atrium, segment of rat aorta precontracted by PGF2 alpha, rat trachea and guinea pig trachea) was estimated in functional experiments. It was established that each of full agonists (acetylcholine, methacholine, carbachol, oxotremorine and aceclidine) has lower affinities for muscarinic M2 receptors of rat atria as compared with its affinity for muscarinic M3 receptors of rat aorta. The partial agonist pilocarpine has similar affinities for muscarinic receptors of rat atria and rat aorta. It was shown that contractile response of guinea pig tracheal smooth muscle is two-staged. It was found that rat and guinea pig tracheal smooth muscle contractions are mediated primarily by muscarinic M3 cholinoceptors and partially by M2 cholinoceptors.