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For many years the focus of neurochemical and pharmacological studies on schizophrenia was on dopamine, and that work yielded a great deal of information about the possible etiology of this debilitating disorder and contributed significantly to the development of antipsychotic drugs. However, it has become increasingly apparent that other neurotransmitters and neuromodulators must also play an important role, and in recent years there has been considerable interest in these other compounds and the systems related to them in the search for developing drugs that are more effective and have fewer side effects than the antipsychotics currently available. This review deals with three of those neurochemicals, namely glycine, D-serine and nitric oxide, and shows how an increased knowledge of them may be important in the future diagnosis and/ or pharmacotherapy of schizophrenia.