Echovirus serotype 11 (ECHO-11) was implicated in three neonatal deaths during an enterovirus outbreak from July through October 1979 in Milwaukee. The deaths followed congenital infections acquired in the community during late pregnancy. Two of the three ECHO-11 and one Coxsackie B4 deaths of infants occurred after cesarean section deliveries. Of 225 confirmed echovirus infections, 30 to 45 percent occurred in infants under 60 days old, 54 to 67 percent in the first year of life, and 13 to 25 percent in the over-10 age groups. In 13 cases with onset of symptoms in the first week of life. 8 (including the 4 fatalities) were acquired congenitally; 6 of the 8 were associated with ECHO-11, 2 with ECHO-7, and 1 with Coxsackie B4. ECHO-7 and 30 other predominant strains were isolated during the outbreak, but none was associated with mortality or severe disease in neonates. At a Milwaukee hospital, a temporal association was observed between echovirus infection, particularly ECHO-11, and increased numbers of stillbirths.