Objective: Atrial fibrillation (AF) is a common source of medical costs, morbidity and mortality. NT pro-brain natriuretic peptide (BNP) is a remarkably strong predictor of AF in older whites; we aimed to assess if this biomarker was as predictive in other racial groups. Design: We used covariate-adjusted Cox model regressions to estimate the HRs of developing AF as a function of NT proBNP, and tested for interactions of NT proBNP with age, gender and race/ethnicity. Setting: The Multi-Ethnic Study of Atherosclerosis (MESA). Patients: 5518 subjects were followed over a median of 7.6 years. During this time, 267 developed AF. Results: NT proBNP was statistically significantly associated with incident AF; for ln NT proBNP, the adjusted HR was 2.2 (95% CI 1.9 to 2.5). Assessed by quintiles, the relationship between NT proBNP was strong and graded; the unadjusted HR for the highest quintile of NT proBNP was 23.7 (95% CI 11.1 to 50.6) and adjusted was 11.4 (95% CI 5.1 to 25.3). NT proBNP was an excellent predictor of incident AF in the younger and older age groups, in men and women and in the different race/ ethnicity groups: the HR for ln NT proBNP as a predictor of incident AF ranged from 2.0 to 3.9 in each subgroup. Conclusions: NT proBNP is a robust predictor of incident AF; its prognostic value is more significant in younger patients and women compared with older patients and men. NT proBNP was also as strongly predictive in black patients, Hispanics and Asian/Chinese as in white patients despite a lower incidence of arrhythmia.