Advances in knowledge of brain neurochemistry have lent impetus to the biological study of schizophrenia. A prominent example is the dopamine hypothesis. Increasing additions to and refinements of neurochemical knowledge, particularly the study of receptors, have continued to support biological hypotheses of schizophrenia. A recently proposed hypothesis is that schizophrenic patients suffer from dopamine receptor supersensitivity at certain phases of their illness. The present article selectively reviews data that are relevant to this refinement of the dopamine hypothesis.