Therapeutic profiles of bromperidol and their relationship with plasma drug concentration and prolactin response were investigated in 30 acutely exacerbated schizophrenic patients treated with randomly allocated fixed-doses of bromperidol (6, 12 or 18 mg/day) for 3 weeks. The mean values (+/- S.D.) of percentage improvement at 3 weeks in total Brief Psychiatric Rating Scale (BPRS) and five subgrouped symptoms were 59.8+/-29.2% for total, 64.6+/-37.5% for positive, 73.3+/-33.7% for excitement, 80.2+/-45.5% for cognitive, 43.1+/-46.5% for negative and 49.6+/-46.8% for anxiety-depression symptoms, respectively. Twenty (67%) of 30 patients were responders defined as having 50% or more symptom reduction significantly greater in responders than those in nonresponders after 2 weeks. Mean plasma bromperidol concentration in patients with 50% or more reduction in positive symptoms was significantly higher than in the others (8.2+/-4.7 vs. 4.1+/-1.8 ng/ml, P< .05). Percentage improvement in total BPRS at 1 and 2 weeks were correlated well with that at 3 weeks. These findings suggest that an early improvement in positive and anxiety-depression symptoms results in favorable outcome of total response to bromperidol treatment. Plasma drug monitoring may have a limited predictive value for improvement in positive symptoms.