SummaryThree cases of portal phlebothrombosis during the puerperium, with infarction of bowel, are described, together with a review of the literature.Possible aetiological factors are discussed. The conjunction of the thrombosis with changes in the blood, particularly the platelets, is stressed.A plea is made that similar cases be reported. Our thanks are due to Mr. R. W. Knowlton, under whose care Cases 1 and 2 were admitted to hospital; to Dr. J. H.Rack, of the department of pathology of the University of Cambridge, for permission to publish Case 3; and to Mr.