Supported by the Canadian Medical Research Council we performed a randomized trial extending from Newfoundland to British Columbia. With others a number of observations showed that aspirin will reduce stroke. With National Institute of Neurological Disorders and Stroke support we learned who would benefit and not from surgery in these stroke threatened carotid diseased patients. We evaluated the upper limits of acceptability of complications beyond which harm was done. Amassing this large data base of approximately 5000 individuals, followed for five years, previously unknown carotid phenomena were observed: 1. Ischemic stroke occurs in patients with prolapsing mitral valves; 2. There is risk of stroke in patients with residual thrombi in the occluded stump of the carotid artery; 3. We detected a lower risk than expected in patients with nearly occluded carotid arteries. We support the contention of Yusuf and Cairns' that Canada needs to give more financial support to purely clinical research. It pays off !