The large proportion of the American Indian population that is under the age of 15 indicates that behavior scientists need to know more about the psychological functioning of children. Epidemiological studies thus far have had a number of limitations. Analysis of these studies suggests future directions for research. An effort should be made to empirically define and standardize diagnostic categories. Complex behavior should be studied with sufficient complexity of analysis. Disorders should be conceived of in terms of the stage of development in which they appear. Diagnoses should be based on the observations of people representing multiple perspectives on the child. Studies should also look at mentally healthy behavior of Indian children..