The effect of methylazoxymethanol (MAM), administered on the 15th gestational day, on the density and pattern of muscarinic cholinergic receptors in some brain areas was assessed using combined radioreceptor binding and autoradiographic techniques. The effect of 15 days' treatment with acetyl-L-carnitine on the same parameter was also assessed. The density of muscarinic cholinergic receptors was found to be increased in the brain of MAM-microencephalic rats. Acetyl-L-carnitine administration caused a significant reduction in the density of receptors under study. A possible role of acetyl-L-carnitine in restoring central cholinergic neurotransmission is discussed.