This experiment was undertaken to determine the efficacy of treating schizophrenic patients by replacement, within practical limits, of their blood with that of normal donors. As far as could be determined, an identical procedure has not been applied previously, although administration of blood and blood constituents has been tried in somewhat different ways. The rationale of the experiment is as follows: Cellular function depends on the structural integrity of the cell, an adequate supply of oxygen and nutrients and the ability of the cell to convert the raw products into essential components of itself or into the specific energy underlying its activity. To the best of current knowledge, the brain cells maintain their structural integrity in schizophrenia. Therefore, there is the possibility that schizophrenia is due to faulty metabolism of the brain cells, either because of a lack of certain essential substances or because of the presence of toxic products