Quality of service and corporate productivity may be improved when employees are formed into semi-autonomous teams that are empowered to be innovative in service and are rewarded for attaining performance goals. This article describes the planned staffing and implementation strategies for three models of primary health care teams (HCTs) in a managed care organization (MCO). Implementation of each model focussed on (1) changes to primary care staffing mix (structural integration of roles) and (2) development of teamwork (functional integration of roles). Evidence from other industries suggests that the planned changes to structural and functional integration of existing primary care delivery models could improve system productivity, patient satisfaction, clinical quality, and employee morale. Retrospective evaluations of whether the planned improvements were achieved, and whether these achievements can be attributed to changes in staffing mix or teamwork, are now being conducted. Opportunities and limitations in conducting these retrospective evaluations are discussed, particularly with reference to use of existing data sources. The article concludes with recommendations for evaluation of natural experiments in primary care redesign.