This invention relates to N-aroyl cyclic amine derivatives of formula (I), wherein X represents a bond, oxygen, NR.sup.3 or a group (CH.sub.2), wherein n represents 1, 2 or 3; Y represents CH.sub.2, CO, CH(OH), or CH.sub.2CH(OH); Het is an optionally substituted bicyclic heteroaryl group containing up to 4 heteroatoms selected from N, O and S; Ar.sup.2 represents an optionally substituted phenyl or a 5- or 6-membered heterocyclyl group containing up to 3 heteroatoms selected from N, O and S and their use as pharmaceuticals, specifically as orexin receptor antagonists. ##STR00001##