The influences of immigration on tuberculosis morbidity in Canada were examined. The pattern of immigration has changed markedly in recent years, increasing proportions of immigrants being from areas other than Europe. Morbidity rates varied widely according to country of birth and were highest among persons born in Asia and lowest among those born in northwestern Europe and the United States. These rates were generally parallel to those reported in the countries of birth, although somewhat lower. Differences in patterns of disease by birthplace were noted, particularly the preponderance of lymphadenitis in Asians and genitourinary tuberculosis in Italians. Although the frequency of drug-resistant bacilli was higher in Asians than in other groups, the vast majority of bacilli in all groups were drug-sensitive. For purposes of tuberculosis control, immigrants from high-incidence countries constitute a high-risk group, and physicians should be aware of this when dealing with patients from these countries.