Direct antiglobulin test (DAT) with only complement detected on red blood cells is a rare laboratory finding, and its significance in the setting of warm autoimmune hemolytic anemia (AIHA) is controversial. During 2 years (2003-2004) 277 patients with positive DAT were recorded in the blood bank registries, 17 of them had DAT reactive with C3 alone with no cold agglutinin or other nonimmune causes for hemolysis diagnosed. Red cell eluate disclosed small amounts of IgG in two patients. In nine patients no signs of clinical hemolysis were found, however, all these patients had underlying conditions that are known to be associated with red cells autoantibodies (autoimmune disorder or malignancy). Eight patients developed AIHA, seven of them with severe hemolysis. Three patients had idiopathic AIHA, and the others have been diagnosed with infectious, lymphoproliferative and autoimmune disorders. In two patients with acute infection the hemolytic process spontaneously resolved, three responded to corticosteroid therapy, while three patients were refractory to two lines of drug therapy and underwent splenectomy. Reticulocytopenia was found in four patients. Our results emphasize that AIHA with DAT reactive with complement alone is a rare disorder and might be accompanied by severe, refractory to conventional treatment and life-threatening hemolysis.