A significant difference of plasma interleukin (IL)-1α concentration was found between schizophrenic patients taking neuroleptic drugs (n = 38) and those not taking them (n = 14; P < 0.02); Kruskal-Wallis analysis revealed a significant difference of plasma IL-6 concentration among the patients taking neuroleptic drugs, those not taking them, and healthy control subjects (H = 7.1, d.f. = 2, P < 0.05); also, there was a significant difference of plasma IL-6 concentration between the patients taking neuroleptic drugs (n = 32) and those not taking them (n = 13; P < 0.01). No significant differences were found between the three groups in the concentrations of IL-1β, IL-2 and tumour necrosis factor(TNF)-α. The present results suggest that neuroleptic treatment may change IL-1α and IL-6 production in schizophrenic patients.