A series of novel tetrahydropyrimidines was synthesized and examined for Ml muscarinic receptor activity. 1,4,5,6-Tetrahydro-5-methoxycarbonylpyrimidine hydrobromide (la; CDD-0034-C) displayed a high affinity for muscarinic receptors in rat brain and stimulated PI metabolism in rat hippocampus. Compound la ameliorated memory deficits associated with lesions of the septohippocampal cholinergic system in rats.