Methods and compositions are disclosed utilizing olanzapine-N-oxide for the treatment of psychosis in humans. Olanzapine-N-oxide exhibits a lessened liability toward drug-drug interactions than olanzapine and a more predictable dosing regimen than olanzapine. Olanzapine-N-oxide is also useful for the treatment of acute mania, mild anxiety states, anxiety disorders, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autistic disorder, excessive aggression, substance abuse, depressive signs and symptoms, tic disorder, functional bowel disorder and fungal dermatitis.