BACKGROUND A growing body of evidence suggests that vitamin D deficiency is associated with increased cardiovascular morbidity and mortality. The present study assessed the association between low serum 25-hydroxyvitamin D (25(OH)D) and coronary artery disease status defined by coronary catheterization findings. METHODS An observational study of 101 consecutive patients admitted to Assaf Harofeh Medical Center during 2009, and scheduled to undergo coronary catheterization was undertaken. Blood was collected for parathyroid hormone, 25(OH)D and high sensitivity C reactive protein (hsCRP). 25(OH)D deficiency was defined as <20 ng/ml. Patients were divided into two groups: patients with normal or non-significant coronary artery disease and patients with a significant coronary artery disease as found during cardiac catheterization. Logistic regression model was used to compare pathological coronary catheterization findings, including 25(OH)D levels dichotomized to low (serum 25(OH)D levels<20 ng/ml) vs. high (serum 25(OH)D levels ≥ 20 ng/ml) and other confounders. RESULTS Patients with pathological coronary catheterization had 25(OH)D deficiency (75% vs 55.1%, p=0.036). Pathological coronary catheterization was more prevalent among patients with 25(OH)D deficiency (Odds ratio (OR) 2.44, 95% confidence interval (CI) 1.05-5.68, p=0.038). This difference was more pronounced after controlling for sex, age, BMI, ethnicity and present smoking (OR 2.92, 95% CI 1.01-8.46, p=0.016). CONCLUSIONS 25(OH)D deficiency is significantly associated with pathological cardiac catheterization findings. This association is strengthened further by controlling for other cardiovascular disease risk factors.