The total protein, albumin, globulin, and immunoglobulin levels of sera from 96 children with homozygous sickle cell disease were studied. A comparison of the results with the levels found in a control group of normal children of the same age shows that the sicklers have higher total protein, globulin, and IgM levels. The amounts of albumin and IgA seen were almost the same in both groups. The IgG levels differed considerably, the sicklers having only about half the quantity seen in normal children.