A 3-month-old infant was exclusively fed a high calorie homemade sesame seed emulsion for 4 weeks. As a result of the milk content, the infant developed hypermagnesemia, hypokalemia, hyponatremia, and hypovitaminosis C. Although the mixture was highly caloric and the infant's intake was good, he showed profound failure to thrive. Analysis of the emulsion indicated that this complication was primarily due to the heterogeneity of the emulsion's caloric content resulting from a settling process which occurred after the emulsion was placed in the infant's bottle. This settling resulted in the portion containing the most calories being the last to reach the infant's mouth. These findings indicate that whenever a vegetarian diet is provided to a bottle-fed infant, the potential heterogeneity of the mixture's caloric content, as well as the contents themselves, should be considered.