Using optical dissector methodology, a morphometric study of numerical density of oligodendroglial cells in layer VI and in adjacent white matter of Broadmann area 10 has been conducted in 23 postmortem brains of schizophrenics and 20 matched controls. Comparing to controls, a significant reduction of numerical density of oligodendroglial cells was found in layer VI (by 31%) and adjacent white matter (by 12%) of schizophrenic patients. The data obtained, as well as ultrastructural signs of oligodendroglial cells apoptosis and necrosis found earlier by the authors, may indicate a loss of these cells in the prefrontal cortex in schizophrenia, which may, in its turn, result in neuronal and high cortical dysfunctions.