The aim of this study was to evaluate two implementation strategies for the introduction of a lifestyle intervention tool in primary health care (PHC), applying the RE-AIM framework to assess outcome. A computer-based tool for lifestyle intervention was introduced in PHC. A theory-based, explicit, implementation strategy was used at three centers, and an implicit strategy with a minimum of implementation efforts at three others. After 9 months a questionnaire was sent to staff members (n= 159) and data from a test database and county council registers were collected. The RE-AIM framework was applied to evaluate outcome in terms of reach, effectiveness, adoption and implementation. The response rate for the questionnaire was 73%. Significant differences in outcome were found between the strategies regarding reach, effectiveness and adoption, in favor of the explicit implementation strategy. Regarding the dimension implementation, no differences were found according to the implementation strategy. A theory-based implementation strategy including a testing period before using a new tool in daily practice seemed to be more successful than a strategy in which the tool was introduced and immediately used for patients.