A concentrate that would retain the virtues of cod liver oil and at the same time permit the giving of a small dose of the substance would be welcomed by infants, parents and physicians alike. Clouse,1 in an extensive treatise on vitamin D, passed over the use of concentrates with the statement that generally cod liver oil can be given, or. if there is need of a concentrate, viosterol should be used. Physicians in private practice do not feel that concentrates can be treated in such casual fashion. One sees too many infants in whom definite rickets develops in spite of the fact that adequate doses of cod liver oil have been prescribed. Babies do not all take cod liver oil willingly in teaspoonful doses, and some do not tolerate the fat in the quantities used if cod liver oil is given. There is, also, more than a groundless suspicion that these infants do not actually receive the amount of cod liver oil advised.Data are accumulating which tend to show, further, that viosterol is not the equivalent of cod liver oil, quantitatively or qualitatively. My experience 2 has been that a group of infants receiving 1,250 units of vitamin D in the form of viosterol was no more protected against rickets than an untreated control group, while a group getting approxi¬ mately the same dose (1,400 units, Oslo) of vitamin D in cod liver oil was protected in 95 per cent of cases. De Sanctis and Craig3 a little later published a similar study which showed that from 1,400 to 1,700 units of vitamin D given as cod liver oil prevented rickets in 97 per cent of the cases studied, while viosterol 100 D in doses of 3,000 rat units daily prevented rickets in only 77 per cent. De Sanctis and Craig cited their own experience to show that rickets develops in from 25 to 30 per cent of infants not receiving antirachitic agents.