To compare the clinical efficacy of haloperidol and risperidone for the treatment of delirium, the authors performed a double-blind comparative study. Twenty-eight patients with delirium were recruited and randomly assigned to receive a flexible-dose regimen of haloperidol or risperidone over 7 days. The severity of delirium was assessed by using Memorial Delirium Assessment Scale scores. Scores for each group decreased significantly over the study period. However, no significant differences in mean Memorial Delirium Assessment Scale scores between groups were found. The group-by-time effect was not significant. In addition, there was no significant difference in the frequency of response to the drugs between the two groups. One patient in the haloperidol group experienced mild akathisia, but no other patients reported clinically significant side effects. These data show no significant difference in the efficacy or response rate between haloperidol and risperidone in the treatment of delirium.