Minimum doses of haloperidol might show similar efficacy and side-effects compared to atypical antipsychotics. The objectives of this study were to compare the efficacy of minimum doses of haloperidol with standard doses of risperidone and olanzapine on a 6-month open trial in first psychotic episode patients and to examine the effect of compliance on their outcome. Forty-two patients were recruited and started on flexible doses of these drugs. Olanzapine was given with no cost to the patients. Efficacy and side-effects were monitored every 3 months using standardized assessments. Thirty patients completed the study. All treatment groups showed improvement in positive, negative and depressive symptoms. There were no differences in side-effects among them. The haloperidol group required higher doses of anticholinergics. The rate of treatment discontinuation was higher in the risperidone group due to the direct cost. Minimum doses of haloperidol might prove to be a good choice of treatment for patients with a first episode of psychosis.