Introduction: Ventricular premature beats (VPB) predict cardiovascular mortality among several adult populations. Controlled dietary magnesium (Mg) depletion studies demonstrated that diminished Mg intake and status induced VPB and other arrhythmias. Thus, we hypothesized that the prevalence of VPB is closely associated with serum Mg concentrations in a general adult population at high cardiovascular risk. Methods: Anthropometric, demographic and lifestyle characteristics were assessed in 750 Cree adults, >18yrs, who participated in an age-stratified, cross-sectional health survey in Quebec, Canada. Holter electrocardiograms recorded heart rate variability and cardiac arrhythmias for two consecutive hours. Multivariate logistic regression was used to evaluate potential associations between serum Mg and VPB. Results: VPB prevalence in adults with hypomagnesaemia (serum Mg ≤ 0.70mmol/L) was over twice that of adults without hypomagnesaemia (50% vs. 21%, p =0.015); results were not materially altered when adults with cardiovascular disease history were excluded. All hypomagnesaemic adults with VPB had type 2 diabetes. Prevalence of VPB declined across the serum Mg concentration gradient in adults with type 2 diabetes only ( p <0.001). In multivariate logistic regressions adjusted for age, sex, community, body mass index, smoking, physical activity, alcohol consumption, kidney disease, antihypertensive and cholesterol lowering drug use, and blood docosahexaenoic acid concentrations, the odds of VPB among diabetics with serum Mg > 0.70 mmol/L was 0.24 (95%CI: 0.06-0.98; p =0.046). Conclusions: Prevalence of VPB significantly declined across the serum Mg concentration gradient in adults with type 2 diabetes, indicating that future interventions to increase levels of serum Mg among adults with type 2 diabetes may confer protection against cardiac arrhythmia.