Neuropathological, neuroimaging, clinical and epidemiological evidence suggests that many cases of schizophrenia are developmental in origin. Dysplastic changes in the medial temporal lobes appear to be of particular importance. However, research implicating a neurodevelopmental origin for schizophrenia has proceeded largely in isolation from knowledge concerning the neurochemistry of the disorder. This paper attempts to integrate these disparate lines of research, and examines the role of trophic mechanisms in the formation of the hippocampus. Those neurotransmitters which have been most consistently found to be abnormal in the temporal lobes of schizophrenics (excitatory amino acids and CCK), are involved in the control of hippocampal development. We suggest that these neurotransmitter findings are the residue of abnormalities in their role as trophic factors in foetal or neonatal life, and that the latter contribute to the developmental aberrations considered fundamental to schizophrenia.