By the use of acetyl- and butyrylthiocholine and α-naphthyl acetate as substrates and selective inhibitors, we have shown the presence of both specific and nonspecific esterases in the myoneural junction of vastus medialis and peroneus brevis muscles of normal subjects as well as in paretic muscles of hemiplegic patients. The presence of nonspecific esterases in human myoneural junction has not been recorded previously. The nonspecific esterases in our fixed tissue were noted to be predominantly E600-sensitive at 10–5 M concentration although resistant at 10–6 M and 5 x 10–6 M concentration.