Background: Recent studies show a mechanistic link between gut microbiota-dependent formation of the atherosclerosis- and thrombosis-promoting metabolite trimethylamine N-oxide (TMAO) and cardiovascular disease (CVD). The clinical utility of TMAO in apparently healthy subjects for predicting incident CVD risks is unclear.Methods And Results: In the EPIC-Norfolk community-based study, we examined baseline fasting levels of TMAO and two of its nutrient precursors, choline and betaine, in a case:control design study comparing apparently European healthy middle-aged participants who subsequently develop CVD (Cases, n = 908) vs those who did not (Controls, n = 1,273) over an ensuing average follow-up period of 8 years.