The comparative sensitivity of acetylcholine receptors of different skeletal muscles--m. masseter, m. gastrocnemius, m. triceps brachii, mm. obliquus et transversus abdominis, mm. intercostales, m. phrenicus to neuromuscular blocking agents was investigated. Experiments were performed on cats anesthetized with urethane (600 mg/kg, i.v.) and chloralose (70 mg/kg, i.v.). Muscle action potentials evoked by electrical stimulation of motor nerves were recorded. Derivatives of alpha-truxillic acid--anatruxonium and cyclobutonium, steroidal neuromuscular blocking agents--pancuronium and pipecurium, decamethonium and succinylcholine and their N-adamantyl analogues--decadonium and diadonium respectively, as well as tubocurarine chloride were tested. It was shown that the succession of relaxation of different skeletal muscles induced by the neuromuscular blocking agents of different chemical structure is variable.