IN a recent communication, Jonxis1 reports quantitative estimations of alkali-resistant and labile haemoglobin in cases of haemolytic disease of the newborn. He comes to the conclusion that after birth only haemoglobin of the labile, adult type is formed, and that in haemolytic disease of the new-born there is a selective destruction of red blood corpuscles containing fœtal haemoglobin. We carried out in the years 1939–42 a great number of similar estimations; these have been briefly reported previously elsewhere2,3.