A rapid ( approximately 90 sec), fully automated method is described for quantifying hemoglobin S (HbS) by high performance liquid chromatography (HPLC) using the Bio-Rad Variant II Turbo analyzer. Although this instrument is designed to quantify only blood hemoglobin A1c (HbA1c), we show that it can also quantify accurately, without modification, HbS levels in sickle cell patients, provided the blood samples meet certain conditions. The samples should contain detectable hemoglobin F (HbF), but should not contain hemoglobin C (HbC). Under these conditions, blood HbS levels obtained by this method correlate well with those obtained by agarose electrophoresis (r(2) = 0.97, n = 81 patients). We also show that quantitation of blood HbF in sickle cell patients is more accurate by this method than by agarose electrophoresis when the HbF level is in the range from 0.2 to 10%.