Severe nutritional deficiencies developed in four infants from a new vegan religious community. They had received breast milk until the age of 3 months; thereafter, breast milk was supplemented with or replaced by extremely low caloric-density preparations. All of the infants had profound protein-caloric malnutrition, severe rickets, osteoporosis, and vitamin B12 and other deficiencies. One infant died, while the three others had an uneventful recovery. After discharge of the infants from the hospital, the community responded well to a modification of the infants' diet, which did not violate their vegetarian philosophy. However, they refused to give their infants vitamin B12 on a regular basis.