Data from the EMBLEM Study, a 2-year, prospective, observational study of health outcomes associated with acute treatment of patients experiencing a manic/mixed episode of bipolar disorder, was used to compare the effectiveness of olanzapine monotherapy versus risperidone monotherapy, and to investigate whether the treatment effects were similar to those reported in a 3-week, randomized controlled trial assessing the same treatments. Symptom severity measures included the Young Mania Rating Scale (YMRS), the 5-item Hamilton Depression Rating Scale, and the Clinical Global Impression-Bipolar Disorder Scale. A total of 245 EMBLEM inpatients were analyzed with YMRS ≥20: olanzapine (n=209), risperidone (n=36). Both the treatment groups had similar improvements in YMRS from baseline to 6 weeks, but there was a significantly greater improvement in 5-item Hamilton Depression Rating Scale in the olanzapine group. There was a similar improvement in Clinical Global Impression-Bipolar Disorder Scale in both the groups and the occurrence of treatment-emergent adverse events and weight gain did not differ between the treatment groups. The EMBLEM results partly support those of the randomized controlled trial, which suggests olanzapine and risperidone have similar improvements in mania but that olanzapine monotherapy may be more effective than risperidone monotherapy in the treatment of depressive symptoms associated with mania. Limitations include differences in study design, patient population, and length of follow-up.