Background: The aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (De Ritis ratio), obtained from AST and ALT activities in the healthy range, has not been studied in association with mortality. Methods: This study included 3392 patients with stable coronary heart disease and aminotransferase activity in the reference range. Patients are categorized into two groups: a group with AST and ALT activity in the healthy range (n= 1697), and a group with AST and/or ALT activity outside the healthy range but in the reference range (n= 1695). The primary endpoint was all-cause mortality at three years. Results: The De Ritis ratio (median 5th–95th percentile] was 0.94 [0.61–1.41] in patients with AST and ALT in the healthy range and 0.93 [0.45–1.96] in patients with AST and/or ALT outside the healthy range (p= 0.700). At three years, there were 86 deaths in patients with AST and ALT in the healthy range: 27 deaths (3.9%) in patients with a De Ritis ratio ≤median, and 59 deaths (8.2%) in patients with the De Ritis ratio >median (adjusted hazard ratio [HR] = 1.16, 95% confidence interval [CI] 0.94 to 1.42;p= 0.159); in patients with AST and/or ALT outside the healthy range, there were 148 deaths: 49 deaths (6.6%) in patients with a De Ritis ratio ≤median, and 99 deaths (14.1%) in patients with De Ritis ratio >median (adjusted HR = 1.27 [1.09–1.48],p= 0.002), with both HRs calculated per unit higher values of the De Ritis ratio. Conclusions: The De Ritis ratio obtained from AST and ALT activity in the healthy range was not independently associated with higher risk of mortality. The De Ritis ratio obtained from aminotransferase activity outside the healthy range (but still in the reference range) was independently associated with the risk of mortality.