This article describes the methods, results and future perspectives of four information sources used to monitor the HIV epidemic in Canada: AIDS case surveillance, HIV case surveillance, HIV sentinel serosurveillance, and behavioral surveillance. Synthesizing data from these multiple sources provides a more comprehensive picture of the HIV epidemic than any one source alone could provide. In Canada, there has been a shift over time from an epidemic dominated by men who have sex with men to one where more than half of new infections are attributed to other groups, such as injection drug users and non-injecting heterosexuals. The available evidence also suggests increasing HIV infections among Aboriginal persons and among women. Surveillance data have been used in Canada to guide prevention and care programs and to formulate policy. In particular, these data have been used to support the development of an HIV testing program in pregnancy, to re-direct community work toward injection drug users and the young, and to demonstrate the effectiveness of new treatments for HIV. The main challenge now is to continue to improve the monitoring of the shifting HIV epidemic with more accurate data and to use the resulting information to inform appropriate prevention and care responses.