Objective: To review recent progress in child and adolescent psychiatric epidemiology in the area of prevalence and burden. Method: The literature published in the past decade was reviewed under two headings: methods and findings. Results: Methods for assessing the prevalence and community burden of child and adolescent psychiatric disorders have improved dramatically in the past decade. There are now available a broad range of interviews that generate "DSM" and "ICD" diagnoses with good reliability and validity. Clinicians and researchers can choose among interview styles (respondent based, interviewer based, best estimate) and methods of data collection (paper and pencil, computer assisted, interviewer or self-completion) that best meet their needs. Work is also in progress to develop brief screens to identify children in need of more detailed assessment, for use by teachers, pediatricians, and other professionals. The median prevalence estimate of functionally impairing child and adolescent psychiatric disorders is 12%, although the range of estimates is wide. Disorders that often appear first in childhood or adolescence are among those ranked highest in the World Health Organization's estimates of the global burden of disease. Conclusions: There is mounting evidence that many, if not most, lifetime psychiatric disorders will first appear in childhood or adolescence. Methods are now available to monitor youths and to make early intervention feasible. (Contains 1 figure and 1 table.)