In Canada, tuberculosis disproportionately affects people who were born abroad. The national tuberculosis medical surveillance programme aims to prevent these cases. These people are referred (referrals) for further in-country surveillance after migration if they have a history of active tuberculosis or have features of old, healed tuberculosis on chest radiograph. Others who are not referred (non-referrals) do not undergo surveillance. In this study we looked at the risk of transmitting TB that comes from referrals and non-referrals. We also compared the transmission rates between the two groups. To make this comparison, we looked at information that Alberta Tuberculosis Registry had about foreign-born migrants (aged 15-64 years). We looked at information about people who came to Alberta between Jan 1, 2002, and Dec 31, 2013. We were interested in cases that had culture-positive pulmonary tuberculosis. We found that the incidence of culture-positive pulmonary disease was nine times higher in referrals than all non-referrals and five times higher in referrals than non-referrals from high-risk countries. Despite a much higher incidence of pulmonary tuberculosis in referrals than non-referrals, referrals were 80% less likely to transmit tuberculosis. But we suggest that instead of focusing only on referrals, Canada could consider screening and treatment of latent tuberculosis in all migrants from high-risk countries.