A pair of male, Negro, fraternal twins are described, both of whom were affected with Rh hemolytic disease. In one twin, the manifestations were typical; jaundice appeared early, exchange transfusion was carried out, and this was followed by prompt and complete recovery. In the second twin, who was treated expectantly, jaundice appeared later and followed the protracted course of the so-called «inspissated bile» syndrome, i. e., the stools were acholic, there was bile in the urine, and most of the serum bilirubin was of the direct reacting type. Of interest was the finding that the occurrence of the syndrome was presaged by the presence of excessive amounts of direct reacting bilirubin in the cord serum. This twin also recovered completely, but convalescence was more prolonged.
The observations on these twins provide further evidence that the constitution of the baby, in addition to the maternal Rh antibody titer determine the nature and severity of the manifestations in an erythroblastotic baby.