This is the first in a series of articles relating results from research which constructed a complete history of interactions with the health care system from available data sources for all patients diagnosed in 1990 with primary breast, colorectal, or lung tumours in Manitoba from one year prior to diagnosis through to two years post-diagnosis. This article presents the motivation and genesis for this line of research. The study evolved from the question of "What happens to a person who is diagnosed with cancer?" into a major research endeavour encompassing a broad spectrum of philosophic and clinical research questions. A large interdisciplinary team collaborated on developing operational methods to combine existing data sources into unified cancer patient histories.