Observations on the deleterious effects of a totally vegetarian diet in infancy are reported and the difficulties encountered in the prevention of nutritional deficiencies in a vegan religious community are discussed. Twenty-five infants of this community who were seen at the hospital showed evidence of protein-calorie malnutrition, iron- and vitamin B12-deficient anemia, rickets, zinc deficiency, and multiple recurrent infections. Evidence of growth retardation was also found in 47 infants seen at the local mother-child health (well-baby) clinic. Samples of breast milk showed low levels of carbohydrate (1.6 to 3.5 gm/100 ml), protein (0.8 to 1.4 gm/100 ml), and fat (2.4 to 4.1 gm/100 ml). The main constituent of the infants' diet after the age of 3 months (a "soya milk" prepared at the community's central kitchen) was extremely dilute with a very low calorific value (13.7 kcal/100 ml). Persistent attempts to find dietary modifications that would satisfy both the vegan philosophy and also the recommended dietary allowances failed. This problem represents a scientific and medicosocial challenge to pediatricians and nutritionists.