EXISTING evidence suggests that the concentrations of IgG immunoglobulin^* in maternal and cord sera are essentially the same. In 1963 von Muralt¹ concluded that no significant difference existed in the absolute concentration of gamma globulin in paired maternal-cord sera after reviewing forty-three published studies in which gamma globulin was quantitated in 1,542 maternal-cord pairs by a variety of methods. Recently, Gitlin et al.² reported cord IgG to be equal to or slightly lower than maternal. They did observe, however, that IgG labelled with iodine-131 was present in higher concentrations in cord than in maternal serum if the iodinated protein had been administered to the mother 25 or more days before parturition. The higher cord ¹³¹I-IgG levels were felt to be a consequence of tracer kinetics and not an indication of higher cord endogenous IgG concentrations².