ABSTRACT
Process evaluation of interventions can address a range of issues, which add to knowledge on outcomes of interventions. Examination of intervention fidelity (whether the intervention is delivered as planned or adapted) is usually central. Other issues include working mechanisms of the intervention, contextual influences, and transferability to other settings. Implementation strategies should be subject of a separate process evaluation, because their content and working mechanisms differ from clinical or preventive interventions. Process evaluation is most informative if its findings can be related to known intervention outcomes. For knowledge accumulation, it is crucial that process evaluation builds on and contributes to theory of implementation in health.
