In the current complex healthcare environment in which organizations are dealing with reimbursement challenges, nursing professional development practitioners must increasingly demonstrate that the time and resources dedicated to educational activities are worth the impact they have on outcomes. Measuring return on investment guides decisions on resources (people, supplies, time) used for professional development activities by showing the financial impact of such activities. The purpose of this project was to review the literature on return on investment for professional development activities to best guide decision-making for limited resources. This is Part I of two articles, the first of which provides a review of the literature. The second article provides guidance for conducting financial analyses of nursing professional development activities.