PIP: The food costs of various infant feeds were examined with focus on how these vary and the cost differences between different feeding patterns in the 1st year of life. The objectives were: 1) to compare prices for branded commercial milk-based products with other types of formulas and breast milk, and with each other according to source of supply, 2) to compare prices of different sources of Beikost (foods other than milk or formulas) used in feeding babies and how these vary by form (home made versus various types of commercially prepared products) and among brands, 3) to review total annual costs of 5 different hypothetical feeding patterns and actual patterns; and 4) to summarize factors other than price which may be significant in the economics and efficiency of infant feeding. National price survey data on a large number of commercial products from several companies producing food for infants were made available for this study. In addition, during June 1976 price surveys were conducted in several large supermarkets, small grocery stores, and drugstores in the Boston area to furnish information on local price differentials. The least expensive acceptable food for an infant was found to be a home made evaporated milk formula. While food costs were quite low, the formula must be prepared, and preparation time was slightly longer than it was with pre-mixed products. Whole milk was the most inexpensive milk-based feed but was undesirable for infant feeding, at least in the early months of life. On a moderate cost diet which supplies the extra nutrients required for lactation primarily from animal resources, lactation ranked in the middle from the standpoint of food cost. The various commercial milk-based feeds were nearly twice the cost of evaporated milk formulas. Concentrated formulas were least expensive, followed by powdered, with ready-to-feed products being the most expensive. Costs of breast feeding for a year ranged from $156 to $281, depending on the diet selected. On the basis of cost per day to meet the infants' needs, the type of product (evaporated milk versus commercial formula in various forms) is responsible for the largest difference in price with the type of packaging of the commercial product as the next most important. Although some savings can be realized on food costs by a changeover to home preparation techniques for Beikost, these savings appear to be much less than those achieved by wise choice of the types of Beikost, regardless of whether the home or commercially prepared foods are used. The proportion of the "baby eating dollar" that is spent for various foods shifts as the baby grows and is dependent on the type of food purchased. In the later months of the 1st year, choice of milk or milk-based feedings, type of commercially prepared or home prepared Beikost, and choice of table foods become most important in determining the overall costs of the infant's diet. The fact that commercial formulas are provided at very low or no cost is probably primary in determining which types and forms of formula hospital services feed infants. Food waste, convenience, cultural acceptability, and cleaning time are among the factors involved in considerations of the best ways to feed infants.