Objective: To compare the efficiency of carbamazepine (CBZ) vs haloperidol (HLP) in the treatment of patients with a bipolar affective manic disorder. Method: we studied 20 inpatients with an acute manic disorder (DSM-III-R) between 18 and 55 years of age. Those who had received psychotropic drugs in the last two weeks, had a physical disorder or showed dangerous and/or disruptive behavior, were excluded. At baseline, the patients were assessed with the Brief Psychiatric Rating Scale (BPRS), the Bech and Rafaelsen Mania Assessment Scale (MAS) and the DiMascio Extrapyramidal Symptoms Scale (DM), thereafter the patients were rated with these scales weekly during five weeks. The patients were randomly assigned to one of two groups: CBZ or HLP. The daily drug doses at the beginning of the study were three identical capsules, each containing 200 mg of CBZ or 5 mg of HLP. If the patient showed a decrease of < 25% in the weekly MAS and BPRS scores, the dose was increased by one capsule per day until a dose of 8 capsules was reached or the therapeutic response was obtained (an improvement in MAS and BPRS scores > 25%). Results: 75% of the subjects were females and the overall mean age was 35.3 +/- 11.1 years. At the beginning of the study, the severity of the symptoms was similar in both groups (MAS: CBZ 30.7 +/- 3.3 vs HLP 27.3 +/- 7.1; BPRS: CBZ 24.2 +/- 8 vs HLP 20.45 +/- 6.8). The one factor ANOVA for repeated measures, showed that the therapeutic response was similar for both groups in the MAS [F(1,13) = 1.02, p = n.s.], as in the BPRS (F < 1). Improvement throughout time, both in the MAS [F(5,5) = 29.98, p < 0.001], as in the BPRS [F(5,5) = 25.42, p < 0.001] were significant. Changes were observed from the first week of treatment (MAS: CBZ 23% vs HLP 30% of improvement; BPRS: CBZ 30% vs HLP 2 3 % of improvement). In contrast, the DM scores showed differences between groups [F(1,13) = 63.16, p < 0.0011; also, the effect of time was significant [F(5,5) = 4.71, p < 0.001]. The final DM scores were: CBZ 0.17 +/- 0.41 vs HLP 4.6 +/- 2.5). Besides, a higher frequency of psychomotor agitation was observed in the CBZ group (50%) than in the HLP group (10%). Conclusions: data shows a similar antimanic effect of CBZ and HLP. This suggests that CBZ might be a first choice treatment in the management of acute manic episodes without significant psychomotor agitation.