In the present work we investigated HDL-C and its subfractions HDL2 and HDL3 as well as total cholesterol (TC), triglycerides (TG), LDL-C, VLDL-C, apolipoproteins A1 (ApoA1) and B (ApoB) and lipoprotein (a) (Lp(a) in 25 patients with newly diagnosed acute lymphocytic leukemia (ALL) before and after induction treatment. The mean basal plasma levels of TC, HDL-C and its subfractions, LDL-C, and ApoA1 were significantly lower than the mean values observed in normal subjects, whereas TG and VLDL-C were significantly higher. The patients (n = 22) who achieved complete remission after chemotherapy showed a significant increase of TC, HDL-C, HDL2, HDL3, ApoA1 and a significant decrease of TG and VLDL-C. These data suggest that ALL patients are characterized by a lipid metabolic derangement mainly of HDL and TG-rich lipoproteins, that is reversed by effective treatment of disease.