Objective: To describe the documented adherence to quality indicators for the outpatient care of attention-deficit/hyperactivity disorder, conduct disorder, and major depression for children in public mental health clinics and to explore how adherence varies by child and clinic characteristics. Method: A statewide, longitudinal cohort study of 813 children ages 6.0-16.9 years with at least 3 months of outpatient care, drawn from 4,958 patients in 62 mental health clinics in California from August 1, 1998, through May 31, 1999. The main outcome was documented adherence to quality indicators based on scientific evidence and clinical judgment, assessed by explicit medical record review. Results: Relatively high adherence was recorded for clinical assessment (78%-95%), but documented adherence to quality indicators related to service linkage, parental involvement, use of evidence-based psychosocial treatment, and patient protection were moderate to poor (74.1%-8.0%). For children prescribed psychotropic medication, 28.3% of the records documented monitoring of at least one clinically indicated vital sign or laboratory study. Documented adherence to quality indicators varied little by child demographics or clinic factors. Conclusion: Efforts to improve care should be directed broadly across clinics, with documentation of safe practices, particularly for children prescribed psychotropic medication, being of highest priority. J. Am. Acad. Child Adolesc. Psychiatry, 2005;44(2):130-144. Key Words: quality of care, child mental health attention-deficit/hyperactivity disorder, psychotropic medication, safety.