Glycosylation is a major pathway for posttranslational modification of tissue protein and begins with nonenzymatic addition of carbohydrate to the primary amino groups. Excessive glycation of tissue protein has been implicated in the pathogenesis of diabetes and ageing. While glycation of aminophospholipids has also been postulated, glycated aminophospholipids have not been isolated. Using normal phase HPLC with on-line electrospray mass spectrometry we found glycated ethanolamine phospholipids to make up 10-16% of the total phosphatidylethanolamine (PE) of the red blood cells and plasma of the diabetic subjects. The corresponding values for glycated PE of control subjects were 1-2%.