A class of pyrrolo\x9b2,3 -b!pyridine derivatives, linked via the 3-position thereof by a methylene group to a tetrahydropyridinyl moiety, the latter moiety being substituted in turn by an aryl- or heteroaryl-substituted divalent monocyclic radical, are ligands for dopamine receptorsubtypes within the body, in particular the D.sub.4 subtype, and are accordingly of use in the treatment and/or prevention of disorders of the dopamine system, including schizophrenia and depression.