The levels of GH, IGF-1, blood glucose and glycosylated plasma proteins (GPP) were determined in sera of diabetics (19 with and 18 without DR, 17 with IDDM and 20 with NIDDM). The levels of the four parameters were significantly higher in diabetics with and without retinopathy compared with controls. Patients with retinopathy had higher levels than those with nonproliferative changes. Serum GH and IGF-1 were higher in IDDM than in NIDDM. In patients with retinopathy, GH was correlated with the duration of diabetes and random blood glucose while IGF-1 did not correlate. It seems that increase GH and IGF-1 levels have possible contribution to the pathogenesis and progression of DR, especially in IDDM besides blood glucose and GPP excess. Such levels do appear to identify diabetics at high risk for rapid deterioration of vision and hence may be useful in selecting those for more intensive therapy.