Arsenic is a potent but modifiable environmental pollutant that has been linked to the increasing global prevalence of high-mortality in Cardiovascular Disease (CVD) (Navas-Acien et al. 2005); arsenic can be removed from drinking water to reduce related health effects. Lactate dehydrogenase (LDH) is used for the evaluation of acute arsenic toxicity in vivo and in vitro (Petrick et al.2000; Peraza et al. 2003; Saad et al. 2006), but is not validated for the evaluation of long-term, chronic arsenic exposure. Various Electrocardiogram (ECG) abnormalities have been observed among cases of acute arsenic poisoning and individuals exposed to excess arsenic through drinking water (Wang et al. 2007). While both LDH elevation and ECG abnormality were previously used as indicators for acute myocardial infarction in clinical practice, their correlation amongst arsenic-exposed subjects was still unclear. Individual variability in human arsenic metabolism has been reported to be an underlying determinant of individual susceptibility to arsenic-induced disease (U.S. EPA 1988). The present study examines the long-term effect of chronic arsenic exposure on plasma LDH levels and ECG abnormality.