In Canada, women (50 to 69 years) undergoing their first screen had a DCIS detection rate of 1.2 cases per 1,000 screens. Women undergoing subsequent screens had a DCIS detection rate of 0.9 case per 1,000 screens. In Canada, women undergoing their first screen had an invasive cancer detection rate of 4.6 cases per 1,000 screens. Women undergoing subsequent screens had an invasive cancer detection rate of 3.7 cases per 1,000 screens. As anticipated, the invasive cancer detection rates were highest among initial screens and also increased in older women and when subsequent screening was not timely.