The Ontario Cancer Treatment Practice Guidelines Initiative was established in 1993 to develop clinical practice guidelines for cancer treatment in Ontario, Canada. First, an organizational structure, consisting of a coordinating committee, a methods resource group, and disease site groups, was put in place. Central to the development of guidelines are the 10 provincial site groups, which use a methodologic framework, the practice guidelines development cycle, to formulate the guidelines. When a preliminary evidence-based recommendation is developed by a site group, it is sent out to a sample of community practitioners for input and is modified based on their feedback. The final product is the practice guideline. Further research is required to determine optimal dissemination strategies and evaluate the impact of these guidelines.