Levels of glycosylated Hb (GHb) are significantly (P < 0.0005) lower in patients with hemolytic anemia (n = 20; mean = 3.9 .+-. 0.1% SD GHb of total Hb) than in patients with nonhemolytic anemia (n = 20; mean = 7.0 .+-. 0.7% GHb) and normal controls (n = 30; mean = 6.7 .+-. 0.7% GHb). A curvilinear correlation between GHb and red cell survival is demonstrable (n = 20; r2 = 0.88; P < 0.001). Determination of GHb may be useful as a screening test for hemolytic anemia and for the evaluation of the degree of hemolysis, provided that diabetes mellitus can be excluded.