Thirty-five patients suffering from schizophrenia, as diagnosed by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, were preselected from 7 clinical trials according to a priori criteria of catatonic signs and symptoms based on 3 Positive and Negative Syndrome Scale (PANSS) items: scores for PANSS item 19 (mannerism and posturing) and either item 4 (excitement) or item 21 (motor retardation) had to exceed or equal 4 at baseline. This particular patient population represents a severely psychotic sample: mean +/- SD PANSS total scores at baseline were 129.26 +/- 19.76. After I week of olanzapine treatment, mean PANSS total score was decreased significantly (-13.14; p < .001), as was mean PANSS total score after 6 weeks of olanzapine treatment (-45.16; p < .001); additionally, the positive subscale, negative subscale, and mood scores improved significantly. A significant improvement in the catatonic signs and symptoms composite score was also observed at week 6 (-4.96; p < .001). The mean +/- SD daily dose of olanzapine was 18.00 +/- 2.89 mg after 6 weeks of treatment. The present data analysis suggests the efficacy of olanzapine in the treatment of severely ill schizophrenic patients with nonspecified catatonic signs and symptoms.