Because of the evidence for increased norepinephrine (NE) production in psychotic patients, we studied the effects of combining the alpha 2-adrenergic agonist clonidine with haloperidol for the treatment of schizophrenic psychosis. Twelve hospitalized schizophrenic patients were taken off their antipsychotic medication for 2 to 4 weeks before double-blind treatment with haloperidol (20 mg/day) combined with either clonidine or placebo. The group receiving clonidine was significantly more improved on the thought disorder subscale of the Brief Psychiatric Rating Scale (p = 0.02). The groups differed initially in the level of negative symptoms, but not controlling for this difference statistically by analysis of covariance did not change the finding with regard to the superiority of combining clonidine with haloperidol. We conclude that larger treatment trials of combining haloperidol with clonidine are warranted.