Echoviruses cause neonatal disease following intrauterine and intrapartum acquisition of the organism or by nosocomial infection. Dizygous twins apparently became infected following transplacental transmission of echovirus 11. At 5 days of age, both twins experienced poor feeding, lethargy and hypothermia, and evidence of coagulopathy and hepatitis. During the sixth week of illness, the convalescence of twin A was complicated by peritonitis and sepsis, and the infant died. Pathologic findings included scattered foci of dystrophic myocardial calcification, distortion of hepatic architecture with fibrous connective tissue surrounding regenerative nodules and large foci of dystrophic calcification, and adrenal hemorrhagic necrosis and calcification. Twin B recovered without sequelae. The disease in twin A was unusual because of the extensive myocardial involvement. Also of interest was the variability of disease in twins who presumably had received a similar inoculum of organism by the same route.