BACKGROUND AND AIM Chronic kidney disease (CKD) and cardiovascular disease are closely interrelated and the presence of one condition synergistically affects the prognosis of the other, in a negative manner. There are surprisingly very few data on the relationship between baseline coronary artery disease (CAD) severity and subsequent decline in kidney function. We aimed to evaluate for the first time whether baseline coronary artery lesion severity predicts the decline in kidney function. MATERIALS AND METHODS The study population was derived from a series of consecutive patients presenting with stable angina pectoris or angina equivalents, who underwent coronary angiography. SYNTAX score for each patient was calculated to define severity of CAD. Change in kidney function was defined by calculating the rates of change in eGFR. RESULTS Among the 823 patients included in our study, the mean age was 59.2±10.7years, 78.4% were males, and 32% had diabetes. The mean baseline eGFR was 87.3±24.9ml/min/1.73m(2) and the median Syntax score was 14 (IQR=10-20). The median length of follow-up was 2.75years (IQR=2.42-3.50). The mean yearly change for eGFR in the entire study population was 4.06 (95% CI: 3.59-4.51)ml/min/1.73m(2). A higher Syntax score was associated with a significantly faster decline in eGFR in all (unadjusted and adjusted) models. During the follow-up, 103 patients developed CKD. A higher Syntax score, analyzed both as continuous and categorical variable, was associated with incident CKD in all models. CONCLUSION We have demonstrated for the first time that severity of CAD is an independent risk factor for the decline in kidney function. Studies are needed to highlight the potential mechanisms regarding the association between severity of CAD and decline in kidney function.