The globin chains of human embryonic, fetal, and adult hemoglobins can be separated by electrophoresis on gels containing polyacrylamide, acid, urea, and Triton X-100. Whole hemolysates are used, and only microgram quantities are required. The order of the major human erythrocyte proteins, from anode to cathode, is zeta, epsilon, carbonic anhydrase, A gamma, delta and G gamma together, beta, and alpha. Protein composition can be measured on Coomassie blue-stained disc gels, and protein synthesis on fluorograms of slab gels containing 3H-leucine-labelled material. These gels have been used to examine the ratio of G gamma to A gamma in blood from fetuses and newborn infants, and to suggest that the switch from A gamma to G gamma during ontogeny may not be linked to the switch from gamma to beta production. beta/gamma synthetic ratios were determined in fetuses at risk for thalassemia. Embryonic and fetal globin synthesis ratios were measured in hemin-induced human erythroleukemia cells K562 in tissue culture. Fetal globin synthesis and the proportion that was of the" fetal" type (G gamma approximately 70%) was studied in erythroid colonies grown in plasma clot cultures from adult, newborn, and 6 month infant specimens. The gels provide a rapid, simple, and inexpensive approach to many problems of globin composition and synthesis.