The incidence of megaloblastic anaemia in 41 cases of twin pregnancy receiving prophylactic folic acid, delivered at the Rotunda Hospital from November, 1960, to November, 1961, is compared with the incidence of megaloblastic anaemia in 42 cases not receiving prophylactic folic acid delivered during the same period. There were no cases of megaloblastic anaemia in the former group, while 7 cases were diagnosed in the latter group. The use of prophylactic folic acid, 5 mg. daily following 32 weeks gestation, is recommended, at any rate in twin pregnancy. [ABSTRACT FROM AUTHOR]