Home blood glucose monitoring has been introduced as a means to achieve good control in patients with diabetes mellitus. Many patients use color-reagent strips and color comparisons to determine blood glucose levels. Intact color vision in the blue-yellow range is necessary for accurately interpreting these strips.Blue-yellow vision deficits occur as a consequence of eye disease and are not genetic or sex-linked. We evaluated blue-yellow vision acuity in 70 diabetic patients and in 19 age-matched control subjects. The patients with diabetes were subdivided according to their degree of retinopathy as follows: no disease (N = 14), nonproliferative diabetic retinopathy (N = 16), proliferative diabetic retinopathy (N = 14) and postlaser-treated (N = 26). None of the control group had deficits. Each group of diabetic patients had a statistically significant increase in color vision deficits compared with the controls. In the laser-treated group, deficits occurred in most patients, were more severe and were significantly increased over all other diabetic subgroups. These deficits may impair visual interpretation of home blood glucose monitoring strips.