Clinicians are frequently faced with the challenge of treating patients diagnosed within the wide spectrum of bipolar depression. Because no one single mood-stabilizing agent can effectively treat depression, and antidepressant agents can trigger mania, these classes are employed together to treat bipolar depression. Because psychotropic medications are frequently mixed in treating a wide variety of psychiatric conditions, clinicians must remain vigiliant for possible drug interactions, which can cause unnecessary morbidity. A case is reported in which a patient suffering from bipolar depression experienced a drug interaction involving sertraline and valproic acid. To date there have been no reported cases of drug interactions between these two psychotropic medications. (Int J Psych Clin Pract 1999; 3: 287-288).