By use of isoelectric focusing in polyacrylamide gel rods we were able to detect traces of HbA (approx. 1%) as a sharp and discrete band. By overloading the gel considerable amounts of HbA (slightly contaminated with HbF) could be detected and isolated. The focused HbA was retrieved from the gels, separated from the carrier-ampholytes and concentrated by a one-step electrophoresis technique. With 3H-leuci ne-labelled haemolysates, after globin chain separation on CM-cellulose, an increase of the beta-chain counts relative to gamma-chain counts was obtained. The study of two cases of high HbF homozygous beta-thalassaemia has demonstrated that this technique may be a valuable tool in detecting minute amounts of HbA mainly in high HbF beta-thalassaemias.