Purpose/Background This study examined the effect of adjunctive minocycline on body metabolism in risperidone-treated patients with schizophrenia. Methods/Procedures Each subject had a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosis of schizophrenia and had been on stable dose of risperidone for at least 4 weeks. In a 16-week randomized, double-blind, placebo-controlled study, subjects received either minocycline (200 mg/d) or placebo. Various metabolic parameters, including weight, waist circumference, fasting insulin, glucose, and lipids, were measured at baseline and week 16. Findings/Results A total of 63 subjects with schizophrenia were enrolled in the study. Fifty-five patients completed week-16 assessments (27 in the minocycline group, 28 in the placebo group). There were no significant differences between the 2 groups in week 16 changes for body weight, body mass index, waist circumference, fasting insulin, glucose, and lipids (P's > 0.300). Implications/Conclusions In the present study, adjunctive treatment of minocycline did not seem to improve body metabolism in patients with schizophrenia receiving risperidone. The implications for future studies were discussed.