The age of susceptibility to poliomyelitis has been of great interest to students of the disease. The problem of fetal infection has been studied by Brahdy and Lenarsky,1 by Kleinberg and Horwitz2 and by Harmon and Hoyne,3 who conclude that in pregnancy there is apparently a failure of fetal infection to occur during the course of poliomyelitis. Cases occur infrequently in the infant under 6 months of age. This may be correlated with the findings of Shaughnessy, Harmon and Gordon4 and of Aycock and Kramer,5 who found that the infant usually shows antibodies if the mother has neutralizing antibodies in her blood. These appear to persist for several months after birth. The incubation time of acute anterior poliomyelitis likewise has been a matter of much discussion among epidemiologists of the disease. The following case histories concern a mother and child who were victims of poliomyelitis