Substituted pyrido[1,2-a]pyrazines of general formula I; wherein Ar and Ar.sup.1 represent various carbocyclic and heterocyclic aromatic rings; A represents O, S, SO, SO.sub.2, CHOH, C.dbd.O, or --(CR.sup.3R.sup.4); and n is 0 2, as well as precursors thereto, are ligands for dopamine receptor subtypes and serotonin (5HT) within the body and are therefore useful in the treatment of disorders of the dopamine and serotonin systems: ##STR00001##