Three important new initiatives in psychiatric epidemiology are reviewed in this paper. The first is a series of epidemiological surveys and community interventions based on the suggestion in previous nonexperimental research that early treatment of child and adolescent mental disorders might help prevent secondary comorbid disorders. The second is a series of epidemiological surveys and interventions aimed at encouraging expanded treatment of mental disorders by demonstrating that mental health treatments can be cost-effective and that expansion of these treatments can represent human capital investment opportunities for governments and employers. The third is a new and innovative set of epidemiological studies of diagnostic boundaries designed to create an evidence base for planned changes over the next decade in the International Classification of Diseases and the Diagnostic and Statistical Manual of Mental Disorders diagnostic systems. (C) 2002 Lippincott Williams Wilkins.