Chronic administration of manganese chloride (5 mg Mn/kg body weight/day) during nine weeks, did not affect the [3H]-quinuclidinyl benzilate binding to muscarinic cholinergic receptors in mouse brain. The quantitation and anatomical distribution of the receptors were determined by autoradiographic methods on coronal sections of midbrain and olfactory bulb. It is concluded that, in our experimental conditions, no alteration in the density of the muscarinic cholinergic receptors is produced in the brain of manganese intoxicated mouse.