ENDS is a world of near infinite diversity in product design, price, appearance, flavors, nicotine strengths. Whilst there is extensive research on the ENDS category and on individual ENDS products only rarely has any attempt been made to compare different devices in terms of their impact o adult smoking behavior. The U.S and U.K. Big Vape Survey is seeking to recruit 130,000 vapers to determine which devices are the most impactful in assisting adult smokers quit attempts. New and established vapers will be surveyed at regular intervals over a 12-month period and questioned in detail about their smoking and vaping behavior. The results of this research will be of interest to manufacturers, consumers, and regulators. This presentation will outline how this study is being carried out, the partner agencies involved, and the unique knowledge gain that will be achieved as the results begin to be available. For the first time adult smokers thinking of switching to vaping will have access to up to date, detailed evidence, on the differential impact of diverse ENDS products thereby enabling consumers to make informed choices about which devices, flavors, and nicotine strengths might best meet their needs. This presentation will provide an update on the first months of data collection.