Phagocytosis of the reticuloendothelial system, measured by clearance of radioiodinated microaggregated human serum albumin, was not significantly different among diabetics, with or without retinopathy, and nondiabetics. The findings are compatible with those of other studies that fail to demonstrate defective antibacterial defense mechanisms in the nonketotic diabetic. Review of tnese studies suggests that any decrease in resistance to infection in the nonketotic diabetic may be due to pronounced hyperglycemia, a remediable factor.