This paper focuses on whether a consistent difference by ethnicity existed in the clinical diagnosis of children and adolescents in two behavioral health service environments and reviews plausible explanations for such a difference. Key measures were clinical diagnosis and ethnicity, abstracted from the administrative dataset of a New Jersey behavioral health care organization during 2000-2002, and a data collection conducted for the State of Indiana during 1991-1992. Sample sizes were 5,394 and 10,437, respectively. Only primary diagnoses were used in this study, classified into externalizing versus internalizing disorders. Logistic regression was performed for the dependent variable of presence/absence of an externalizing disorder or internalizing disorder. A main effect for ethnicity was found; African American youth received more externalizing diagnoses than did European American youth (odds ratio 2.01 (CI: 1.73-2.33) in one sample and 1.67 (CI: 1.44-1.94) in the other); African American youth also received fewer internalizing diagnoses than European American youth (odds ratio 0.55 (CI: .48-.63) in one sample and 0.75 (CI:.64-.88) in the other. Potential explanations for these findings include: 1. Biopsychosocial origin; 2. Clinician bias; 3. Discordant normative behavioral expectations between parents and service providers; and 4. Interaction between differential expression of underlying pathology and tolerance for such expressions.