This paper chronicles the role of British Columbian provincial authorities and medical practitioners in engineering the deportation of psychiatrically disordered and cognitively disabled immigrants out of the province between Confederation and 1939. Approximately 750 mental patients were removed from BC during the 1920s and 1930s alone, and more than 5000 had been deported from the country as a whole by the outbreak of World War II. With the use of provincial and federal government records and correspondence, institutional documents, print media clippings and patient files, I probe the professional practices and discourses that fuelled this movement to banish asylum inmates. Across these seven decades, medical authorities, in alliance with bureaucrats and various anti-immigration forces, succeeded in assembling a powerful and efficient system for screening out and expelling those new Canadians who ostensibly failed to meet the mental standards for Canadian citizenship. Bolstered by theories of eugenics and race betterment, and drawing on public fears about the unregulated influx of aliens and the associated scourge of madness, officials turned to deportation as an expedient means for ridding hospitals of their least desirable denizens. I argue more generally that the deportation of ‘insane’ and other ‘unfit’ immigrants was nourished by the flood ofnativist, rac(ial)ist, exclusionist, eugenist, and mental hygienist thinking that dominated British Columbian and Canadian political and public culture throughout this ‘golden age’ of deportation.