This article discusses the role of formative and process evaluation in the development and implementation of a pilot intervention to improve the identification, treatment, and referral of women abused by their partners who present to an emergency department (ED). These evaluations were undertaken in conjunction with an outcome evaluation of training in and use of a five-step protocol of care piloted in a New Zealand public hospital. The outcome evaluation showed there was an improvement in identification and acute care of abused women following the intervention. The article highlights key factors that were relevant to the intervention's development and implementation, including social context, development processes, appropriateness for the setting, and level of support from key stakeholders. Factors identified as key to intervention effectiveness included its appropriateness for abused women and responsiveness to specific hospital, department, and staff needs. The key role of formative and process evaluation in the development and implementation of pilot interventions is highlighted, and the particular lessons gained from this study have relevance and application to other interventions.