A microchromatographic procedure (Isolab Fast Hb Test System) which was developed for the quantitation of Hb AI (10) has been found useful for the quantitation of Hb F in samples that contain Hb S and/or Hb C but no Hb A (% Fmicro). This method has been evaluated through analyses of known mixtures of Hb F and Hb S. The Hb Fmicro levels in patients with sickle cell anemia and related conditions were compared with results obtained by alkali denaturation (% FAD) and conventional DEAE-cellulose chromatography (% FDE). This microchromatographic technique is a fast, simple, and sensitive method for Hb F quantitation in patients with Sickle cell disease.