The motor end plate of the cat posterior cricoarytenoid muscle is examined by using electron microscope and histochemical method. Furthermore, we studied the localization of acetylcholine receptors by fluorescent staining of snake neurotoxins (alpha-bungarotoxin and erabutoxin b) and autoradiography of 125I-labeled alpha-bungarotoxin. The fine structure of the motor end plate of this muscle is approximately identical to that of other singly innervated skeletal muscles. The subneural apparatus is activated by cholinesterase (ChE). ChE reaction appears markedly in primary and secondary synaptic clefts. No remarkable difference is found between TMR-labeled neurotoxin and FITC-conjugated neurotoxin. Fluorescent staining is associated with subsynaptic muscle membranes and not with motor nerve terminals. The autoradiogram revealed heavy accumulations of grains at the junctional folds.