Many studies of clinical populations have reported significant differences between whites and blacks in prevalence rates of mental disorders. However, data from the Epidemiologic Catchment Area study indicate only modest differences. The author describes factors in the treatment experiences of black and white patients that may lead researchers to find questionable disparities in prevalence rates. These factors include racial differences in treatment-seeking behavior, likelihood of involuntary commitment, representation in research samples, presentation of psychiatric symptoms and resulting diagnoses, and accuracy of psychological tests as well as disparities in treatment. The author suggests guidelines for improving research methods and designs, including documenting the ethnic composition of samples and using structured diagnostic assessments, so that unintended inequalities can be identified, addressed, and monitored and the accuracy of prevalence data among blacks can be improved.