Unusual increases in the minor hemoglobin components (Hb AIa, b, c) known to be elevated in diabetes mellitus were found in states of relative or absolute insulinopenia: diabetic ketoacidosis, steroid-induced diabetes, insulin-dependent diabetes in cystic-fibrosis patients, and cystic fibrosis occurring in infants who have a marked suppression of insulin secretion. In ketoacidotic diabetics, it required at least a month for high Hb AI levels (16.9 +/- 2.6 per cent) to stabilize at nonacidotic levels (12.8 +/- 0.3 per cent), suggesting that decreases occur only as new red cells form under conditions less favorable to Hb AI synthesis. Abnormal amounts os Hb A and Hb AI resisted removal from diabetic red-cell membranes by low ionic buffers but yielded to hypotonic Tris buffer. Their removal resulted in simultaneous elution of peripheral and integral membrane proteins. It is suggested that Hb so firmly bound could reduce membrane elasticity and cell deformability, characteristics so vital to normal red cell movement through the microvasculature.