Although historically research findings about racial and ethnic issues were all too often used to support prevailing concepts of racial inferiority, in recent years racial and ethnic factors have frequently been ignored. However, current findings suggest that racial and ethnic differences exist in the symptom presentations of psychiatric disorders. Significant racial differences have been noted among proposed biological markers for various psychiatric disorders, such as serum creatinine phosphokinase, platelet serotonin, and HLA-A2. Racial and ethnic differences in response to psychotropic medication, such as higher blood levels found among Asians, affect dosage requirements and potential side effects. All of these developments underline the importance of considering ethnic and racial factors in psychiatric research.