Background: Systematic reviews (SRs) are critically important to support decision making in health care. Interest in reliable and quick evidence synthesis has sparked development of “rapid reviews” yet no clear consensus exists on what these are or what processes they use. The goal of this project was to understand and describe practices of conducting rapid reviews. Methods: We searched the literature to identify rapid review methods, guidance, and empiric evidence, and conducted interviews with organizations that produce rapid reviews to identify current practices, and understand the evolution of their programs and products. We analyzed the data qualitatively, integrating information gathered from the literature and interviews. Results: We identified 36 rapid products from 20 organizations (production time, 5 minutes to 8 months). Almost all products used four approaches to save time (restricted database searching, inclusion criteria, data abstraction, and dual review); with faster products tending to employ more of these approaches. Methods also varied by synthesis type, with some products (Inventories) avoiding synthesis completely, while others (Rapid reviews) performed syntheses similar to full reviews but with limited scope and review to achieve deadlines.  Interviews with producers provided insight into these variations. Most rapid products are produced to support specific decisions in an identified timeframe within the context of a close relationship between researcher and end-user. This allows selection of methods that best fit the decision and timeframe, and helps the end-user understand resulting limitations. Almost no empiric evidence exist comparing rapid reviews and SRs. Conclusions: Rapid products have tremendous methodological variation, but categorization based on timeframe or type of synthesis reveals some patterns. This variation in methods results in part from the close relationship between reviewer and end-user. Organizations considering production or consumption of rapid review products need to consider this context and other factors.