Background: Total white blood cell count (TWBCc), an index of chronic and low-grade inflammation, is associated with clin. symptoms and metabolic alterations in patients with schizophrenia.The effect of antipsychotics on TWBCc, predictive values of TWBCc for drug response, and role of metabolic alterations require further study.Methods: Patients with schizophrenia were randomized to monotherapy with risperidone, olanzapine, quetiapine, aripiprazole, ziprasidone, perphenazine or haloperidol in a 6-wk pharmacol. trial.We repeatedly measured clin. symptoms, TWBCc, and metabolic measures (body mass index, blood pressure, waist circumference, fasting blood lipids and glucose).We used mixed-effect linear regression models to test whether TWBCc can predict drug response.Mediation anal. to investigate metabolic alteration effects on drug response.Results: At baseline, TWBCc was higher among patients previously medicated.After treatment with risperidone, olanzapine, quetiapine, perphenazine, and haloperidol, TWBCc decreased significantly (p < 0.05).Lower baseline TWBCc predicted greater reductions in Pos. and Neg. Syndrome Scale (PANSS) total and neg. scores over time (p < 0.05).We found significant mediation of TWBCc for effects of waist circumference, fasting low-d. lipoprotein cholesterol, and glucose on reductions in PANSS total scores and PANSS neg. subscale scores (p < 0.05).Conclusion: TWBCc is affected by certain antipsychotics among patients with schizophrenia, with decreases observed following short-term, but increases following long-term treatment.TWBCc is predictive of drug response, with lower TWBCc predicting better responses to antipsychotics.It also mediates the effects of certain metabolic measures on improvement of neg. symptoms.This indicates that the metabolic state may affect clin. manifestations through inflammation.