Human globin chain separation, a key procedure in the study of hemoglobinopathies, is routinely performed by chromatography on carboxymethylcellulose. This method, though relatively easy and highly reliable, is expensive and time consuming. A new procedure, based on isoelectric focusing, is presented which allows the simultaneous separation of globin chains from multiple samples (at least 20 per gel slab). The method is rapid, inexpensive and can be easily carried out in clinical laboratories, and its high sensitivity allows the identification of radioactive bands even with minute amounts of labelled material. A new phenomenon, called the 'Nonidet P-40 effect', which greatly enhances the separation between gamma and beta chains by binding to these two chains and shifting their pI values in opposite directions, is described.