Peripheral blood lymphocyte subsets and serum immunoglobulin levels were assessed in 42 patients and 37 healthy controls. 24 patients were free from neuroleptic medication and 15 had never been treated with neuroleptics. 31 patients had a diagnosis of schizophrenia (DSM-III criteria) and 11 a diagnosis of a disorder of the schizophrenic spectrum. As compared to healthy subjects, the drug naive schizophrenic patient group showed an increase of T suppressor lymphocytes, while the drug-treated schizophrenic group showed an increase of T helper lymphocytes. The drug-treated schizophrenic group differed from the drug naive one relative to a decrease of T suppressor lymphocytes. As compared to healthy subjects, the drug naive spectrum disorder patients showed an increase of absolute number of lymphocytes, while the drug treated spectrum group showed an increase of B lymphocytes. These findings did not correlate with any clinical or neuromorphological variables taken into account.