(1) The D.P.A.G. test is a sensitive, simple and inexpensive test. In 84%of jaundiced ABO heterospecific cases the test indicated that the foetal cells had been sensitized by the maternal iso-agglutinins. (2) The PCV estimation of foetal blood was found to be of little value as a diagnostic aid, except in cases of severe ABO haemolytic disease where it was found to be below normal. (3) Morphology of the red blood cells proved disappointing as a diagnostic measure in our hands. In my opinion the tests of choice for a diagnosis of ABO haemolytic disease are the ABO and Rhesus groups of the mother and child, the D.P.A.G. test, and a bilirubin estimation of the cord blood or venous blood of the child.