The Digitalis Investigation Group (DIG) trial was a large simple clinical trial that involved 302 participating centers in the United States and Canada. In order to encourage participation by Canadian investigators, to provide additional help to what were expected to be largely research-inexperienced investigators in Canada, and to provide the study's data coordinating center with resources in Canada to deal with potentially different rules, regulations, and cultural differences, regional coordinating centers were established in four regions of Canada: the maritime provinces, Quebec, Ontario, and western Canada. Canadian centers recruited significantly better than their U.S. counterparts and had slightly better retention and follow-up. While it is not possible to declare that the regional coordinating centers were responsible for this improvement, it is believed that these regional centers did play a role. This role included being able to identify investigators who could be expected to do well, providing one-on-one training and instruction to investigators, and being able to solve problems and implement change in the relatively fewer centers in their regions. The regional coordinating center also reduced the intensity of the workload on the data coordinating center by serving as the primary point of contact for Canadian investigators. The use of regional coordinating centers in studies with a large number of participating centers is highly recommended.