BACKGROUND. Fractal analysis provides a global index of the geometric complexity and optimality of vascular networks. In this study, we investigated the relationship between fractal measurements of the retinal vasculature and chronic kidney disease (CKD). METHODS. This was a population-based case-control study which included participants from the Singapore Prospective Study Program. We identified 261 participants with CKD, defined as estimated glomerular filtration rate of <60 mL/min/1.73 m(2), and 651 controls. The retinal fractal dimension (D(f)) was quantified from digitized fundus photographs using a computer-based programme. RESULTS. The mean D(f) was 1.43 +/- 0.048 in the participants with CKD and 1.44 +/- 0.042 in controls (P = 0.013). Suboptimal D(f) in the lowest (first) and highest (fifth) quintiles were associated with an increased prevalence of CKD after adjusting for age, systolic blood pressure, diabetes and other risk factors [odds ratio (OR) 2.10, 95% confidence interval (CI) 1.15, 3.83 and OR 1.84, 95% CI 1.06, 3.17; compared to the fourth quintile, respectively). This association was present even in participants without diabetes or hypertension. CONCLUSIONS. Our study found that an abnormal retinal vascular network is associated with an increased risk of CKD, supporting the hypothesis that deviations from optimal microvascular architecture may be related to kidney damage.