Infants who die of hypernatremic dehydration usually demonstrate at autopsy an underlying condition or disease process that predisposes to increased water loss. In the absence of such findings, forensic concerns may focus sharply on parental or caretaker neglect as an underlying cause of death. In this case report, we describe unrecognized fatal hypernatremic dehydration in two exclusively breast-fed neonates due solely to failure of maternal lactation. We further describe epidemiologic and etiologic features of such deaths and discuss forensic difficulties encountered in their certification.