ABSTRACT Objective: To study the patterns of psychotropic drug prescription for patients with diagnoses of bipolar disorder and schizophrenia. Method: I examined data from the Ullevål 600 Study (321 pharmacologically stable outpatients with DSM-IV psychotic disorders), and compared the patterns of psychotropic drug prescription within the two major diagnostic groups and with the official guidelines. Results: Psychotropic drugs are prescribed on a large scale to pasients with serious mental illnesses. The governing guidelines are usually followed, with some exceptions. Unexpectedly, findings show that lamotrigin is the most widely used mood-altering drug. It is also surprising that polypharmacy is a widely used practice, as there are several side effects and lack of supported positive effect.Conclusion: All in all, I find very few discrepancies with regard to patterns of psychotropic drug prescription within the two groups, a result which conveys that the illnesses might be closer related than previously assumed.