Antipsychotic drugs, frequently used for treating schizophrenia, have many unpleasant and sometimes life threatening side effects. Some of these side effects, such as agranulocytosis cannot be explained satisfactorily on the basis of the drugs’ pharmacological actions. The first indication of this event is neutropenia which then progresses to full blown agranulocytosis. This study was carried out to quantitatively assess neutrophil maturity in patients on antipsychotic drugs using the appearance of their granules on electronmicroscopy. Blood samples were collected from schizophrenic patients (n:20) before and six weeks after starting treatment with two types of Antipsychotic drugs (Risperidone and Chlorpromazine) and from healthy subjects (n:21) having no history of antipsychotic drugs medication and processed for transmission electron microscopy. Volume density of azurophilic (electron-dense) granules in patients after treatment was found to be greater than both before treatment and in control group. The volume weighted mean volume of granules was significantly greater in cells of patients after treatment. There were significantly more neutrophils with fewer than three lobes of nuclei in patients after treatment than in controls or before treatment. These findings suggest neutrophil cellular immaturity in the patients during 6 weeks of treatment even though there was no haematological evidence of neutropenia. It is suggested that immaturity of neutrophils manifests before any evidence of neutropenia.