Two unrelated female infants with homozygous protein C (Pr C) deficiency are reported. Both are of U.K. Pakistani origin and in each case the parents are consanguinous. A previous sibling had died in each family. Both sets of parents were shown to be carriers. The concentration of Pr C in both infants was low at birth. Both developed necrotic skin lesions (purpura fulminans) and responded well to Pr C concentrate. Both are developing normally although one has visual impairment due to retinal artery thrombosis which occurred before treatment was commenced. Both infants are treated with intravenous Pr C concentrate administered daily by the parents at home. Studies of the half-life of exogenous Pr C in one of the patients has shown an increase from 2.7 to 10.8 h during the course of treatment thus enabling it to be administered once daily while still maintaining effective plasma concentrations. In the other patient half-life has fluctuated but Pr C is also given once daily. This is the first report of this condition being treated in this way in the United Kingdom.Infusion of Pr C is a safe and efficient way of treating infants with homozygous Pr C deficiency in the medium term.