Serum lactate dehydrogenase (LDH) is known pathologic marker for a diversity of diseases, including myocardial ischemia. Strenuous and enduring physical activity can transiently induce a greater total LDH level, still within its normal range. To date, however, it has not been determined whether normal-range LDH might be inversely associated with coronary artery disease (CAD) in the low-cardiovascular-risk, physically active, adult population. We conducted a retrospective cohort analysis. A total of 5,519 healthy adults aged 34 to 86 years were followed up for a mean period of 4.2 years. The cohort incidence of CAD was 6.1% (338 cases) from 2001 to 2009. In the present cohort, greater mean LDH levels were significantly associated with a greater number of years, days/week, and minutes/week of leisure time activity (p = 0.02, p = 0.04, and p = 0.01, respectively). These associations were externally validated successfully by analysis of all 5,064 healthy participants aged <40 years with normal-range LDH from the 2007 to 2010 National Health and Nutrition Examination Surveys combined. For instance, the mean LDH level was significantly greater in those engaged in 6 to 7 versus 1 to 5 days/wk of vigorous-intensity work activity (138.0 ± 20.7 IU/L vs 133.3 ± 21.7 IU/L, respectively, p = 0.007). In our cohort, the hazard ratio for CAD according to the normal total serum LDH tertiles, adjusted for multiple risk and protective CAD factors in a Cox proportional hazards model, was 0.70 (95% confidence interval 0.54 to 0.92) in the greater versus lower tertile (p for trend = 0.01). In conclusion, we suggest that increased normal-range total serum LDH is associated with reduced short-term risk of CAD outcome in this low-risk, physically active population.