We review the empirical research on Free/Libre Open Source Software (FLOSS) development and assess the state of the literature. Our review is organized around an input-mediator-output-input (IMOI) model. We start with a description of the articles selected for the review. We then discuss findings of this literature categorized into issues pertaining to inputs (e.g., member characteristics, technology use and project characteristics), processes (software development and social processes), emergent states (e.g., trust and task related states) and outputs (e.g. team performance, FLOSS implementation and project evolution). Based on this review, we suggest research questions, including methodological and theoretical issues, to guide future inquiry in this area.