Diabetic retinopathy is a sight-threatening complication of the retinal microvasculature. While important environmental factors have been clearly identified as influencing its development, increasing evidence suggests that diabetic retinopathy has a genetic component. A variety of studies have explored associations between candidate genes and frequency and severity of retinopathy. Overall, this review has found that the majority of candidate genes studied exhibit weak or no association with retinopathy status, and where associations have been detected these results have not been replicated in multiple populations. This may reflect inaccurate case definition, small subject numbers and possibly inadequate markers for genetic studies.