1. Erythrocyte hemolysates from hematologically normal, adult individuals were studied by means of starch block electrophoresis.
2. The electrophoretic patterns obtained indicated the presence, in addition to the main component of A hemoglobin A1, of three other hemoglobin fractions designated as A2, A3 and A4, A2 and A4 move slower, while A3 moves faster in alkaline buffer. These components were isolated by elution from the starch after separation by electrophoresis.
3. The concentrations of the various fractions in the hemolysates were estimated from a sample of normal individuals investigated.
4. In our experiments, electrophoretic patterns obtained on starch that has been re-used as a supportive medium for electrophoresis were somewhat different but comparable to those obtained on starch that was used for the first time as a supportive medium; these differences are discussed.
5. Some characterizations of the isolated components are made.