Previous studies have reported the use of globin chain-specific complementary DNAs to quantitate the amount of human globin mRNA and human globin genes in normal and abnormal cells. In order to obtain larger amounts and more purified globin mRNAs as templates for these experiments, preparative polyacrylamide gel electrophoresis in formamide has been used to separate alpha- and beta-globin mRNA from polyadenylate containing RNA of human reticulocytes. Fifty to one hundred-fifty micrograms of RNA can be applied to the preparative gel and the recovery of the globin mRNA is about 50%. The isolated alpha- and beta-globin mRNAs were assayed in a wheat germ cell-free system, and the alpha- and beta-globin synthesized quantitated by cellulose acetate electrophoresis. The purified alpha- and beta-globin mRNAs direct globin synthesis which is more than 90% either alpha- or beta-globin, respectively. The cDNAs prepared using each of the isolated mRNAs as template are also shown to be specific for alpha- or beta-mRNA sequences. The gel electrophoresis technique used permits the relatively large scale isolation of alpha- or beta-globin mRNAs from human cells.