The purpose of this paper is to evaluate the implementation of the Move to Improve worksite physical activity program using a four step framework that includes the following: (i) defining the active ingredients, (ii) using good methods to measure implementation, (iii) monitoring implementation and (iv) relating implementation to outcomes. The intervention active ingredients consisted of a goal setting behavior change program, a team competition and environmental supports. Intervention fidelity and dose were measured by surveys administered to site co-ordinators, team captains and employees. Implementation was monitored by the use of biweekly assessments that tracked individual physical activity levels and through weekly reports of the project director and site co-ordinators. Latent growth modeling was conducted to determine whether intervention outcomes were affected by site implementation (i.e. fidelity) and/or participation by employees (i.e. dose). Results showed high levels of intervention fidelity, moderate to high levels of intervention dose delivered and moderate levels of the intervention dose received. Level of implementation affected the degree of change in vigorous physical activity (Mean = 5.4 versus 2.2; chi(2) = 4.9, df = 1), otherwise outcome measures were unaffected by fidelity and dose. These findings suggest that practitioners should focus more energy assuring that the core components are fully implemented and be less concerned about the level of participation.