Isolated case reports have suggested short-term beneficial effects of subcutaneous insulin infusion pump treatment on background and proliferative diabetic retinopathy. To evaluate this question further, 30 eyes of 15 Type I diabetic patients were evaluated prospectively before and after 11–23 months (mean 18.1 months) of pump treatment. In each patient plasma glucose and total glycosylated hemoglobin fell to normal or near normal levels. The ten eyes without diabetic retinopathy at entry remained without. Four of 20 eyes with diabetic retinopathy at entry advanced by modified Early Treatment Diabetic Retinopathy Study (ETDRS) classification, including one eye that progressed from background to proliferative diabetic retinopathy. No eyes with diabetic retinopathy improved their modified ETDRS classification. One eye progressed to blindness; no other eye lost vision. Six eyes had laser treatment prior to insulin pump treatment; four of these and two more required laser during pump treatment. Two eyes had vitreous hemorrhages prior to pump treatment; one of these and four others hemorrhaged during pump treatment. No eyes with diabetic retinopathy showed regression of microvascular changes. The data suggest prolonged restoration of near normal glucose metabolism with the insulin pump does not reverse established diabetic retinopathy. Whether pump treatment slows the progression, or prevents the development, of diabetic retinopathy remains to be established.