Innovation and diffusion of new surgical procedures are limited in Manitoba, Canada by restrictions on which hospitals are allowed to perform particular surgical programs. Programs centralizing performance of certain operations in a few hospitals have the potential for controlling costs and quality of care but may limit access for individuals living in other areas. Such issues are highlighted in this analysis of coronary artery bypass graft surgery in Manitoba. Patterns of growth and access are first examined; then regional variations in rates of bypass surgery are compared with rates for coronary angiography and valve surgery. Physician reluctance to refer patients to Winnipeg appears to be responsible for the lower rates of these procedures in Western Manitoba. The implications for studies of centralization/regionalization of medical services, physician decision-making, and diffusion of technology are explored.