The paper begins with an overview of the literature and criminological or sociological theories that purport to explain the level and pattern of immigrant criminality. It then examines data on Canada's most serious offenders. The study used the records of those incarcerated in Canada's Federal prison system to estimate and compare crime rates for the foreign and native-born populations. The study concludes that if levels continue at their current rate, Canada will add approximately 2.5 million people to its population through immigration this decade. This constitutes almost 10 percent of the existing Canadian population. The study found that, so long as care is taken, these levels of immigration will not contribute to any disproportionate increase in serious crime in Canada. In fact, if future immigrants show no greater propensity toward crime than those already in the country, the ratio of tax payers to criminals should become more favorable. Despite the disruption of social structures, barriers to opportunity and cultural conflict which they face, the foreign born are clearly underrepresented among Canada's serious criminal population. Steps should be taken, however, to ensure that all immigrant groups are integrated into Canadian society, have access to opportunities, and trust institutions. Immigrants from the Caribbean and Latin American countries seem to be in special need of efforts in this regard. 4 tables and a 30-item bibliography