The field of psychiatric epidemiology has a long, albeit often neglected, history-one that antedates the beginning of psychoanalysis. Klerman (1) and Weissman (2) have outlined 5 generations of epidemiologic research. The first dates back to 1885, when Jarvis (3) used hospital records and key informants in a Massachusetts town to determine the prevalence of treated and untreated mental disorders. The post-World War II era, which Weissman and Klerman both referred to as the golden age of psychiatric epidemiology, saw the famous Midtown Manhattan Study (4) in the US and the Stirling County Study in Canada (5). These studies and others were marked by large representative samples, high response rates, and the use of measures of overall impairment rather than the unreliable psychiatric diagnoses of the day. The third era saw the introduction of structured clinical interviews, such the Present Status Schedule (6) in the US and the Present State Examination (7) in the UK; the Schedule of Affective Disorders and Schizophrenia (8); the Diagnostic Interview Schedule (9); the Composite International Diagnostic Interview (10); and numerous others. These interviews were accompanied by more objective and reliable criteria for the various diagnostic categories, first manifested in the Research Diagnostic Criteria (11) and leading eventually to the DSM-III and its later modifications. The Epidemiologic Catchment Area study (12), which involved over 18 000 adults in 5 sites and used the Diagnostic Interview Schedule, is perhaps the prime example of this generation of research. The fourth generation melded the previous generation's methodological developments-objective diagnostic criteria and structured interviews-with probability samples that encompassed an entire country, such as the National Comorbidity Study in the US (13) and the Community Health Survey in Canada (14). The fifth generation, which is still relatively young, focuses on children and adolescents. Canada has been a major player in this area and has produced many leaders, including Alec Leighton and Jane Murphy in the Stirling County Study (5); Roger Bland with the Edmonton studies (15); the late Dan Offord, who led the Ontario Child Health Survey and the Ontario Health Supplement (16,17); and the researchers who conducted the Quebec Child Mental Health Survey (18). Each of these studies marks an important stage of development in Canadian psychiatric epidemiology, yet all share a common element: they were conducted in a specific region. Consequently, we have not to date had any national estimates of the prevalence of major psychiatric conditions in this country. The Canadian Community Health Survey (CCHS) Cycle 1.2 remedies this, being a study of the entire country. As will be explained in this issue's articles, it continues a long tradition of community surveys undertaken by Statistics Canada. The CCHS Cycle 1.1 yielded some data regarding the presence of psychological problems; however, its limitations in this regard prompted Cycle 1.2, whose major focus was on factors that predisposed people to or protected them from such problems. At the 2002 meeting of the Canadian Academy of Psychiatric Epidemiology (CAPE), representatives from Statistics Canada outlined the design of CCHS 1.2 and announced a joint Canadian Institutes of Health ResearchStatistics Canada grant competition to analyze the data. The CAPE members decided to collaborate in their submissions rather than compete against each other for a limited number of grants, with very gratifying results in that a significant proportion of the grants were awarded to them. The entire 2004 CAPE meeting, which was held just prior to the annual Canadian Psychiatric Association meeting, was devoted to presentations of the results. The Journal's Editorial Board agreed to devote one issue to those papers. To save space, a single article (see the paper by Gravel and Beland, 19) presents the methods used by all. …