In the past, schizophrenia research has focussed on mono-aminergic systems, particularly dopaminergic systems. Less is known about the contribution of non-monoaminergic systems in the pathology of schizophrenia. The significance of non-monoaminergic systems, like excitatory aminoacids, cholecystokinin, s -receptors and g -type endorphins, for schizophrenia research are discussed. Several trials have been performed with cholecystokinin and g -type endorphins. The results of open and single blind experiments with these peptides were promising. However the outcome of the first double-blind, placebo-controlled, studies were less positive. In both cases there are not enough double-blind, placebo-controlled studies available to give a definite judgement about the role of these peptiden in the pathology of schizophrenia. Far less studies have been done with s -receptors antagonists and excitatory aminoacids. Therefore more trials with s -receptors antagonists and excitatory aminoacids are needed to establish the role of these systems in the pathology of schizophrenia.