This document compares the benefits and risks of breastfeeding in light of recent evidence that mothers' milk contains high levels of chemical contaminants. Information is presented on the occurrence and toxicity of agricultural and industrial chemicals found in breast milk and on the lead, industrial chemicals, nitrates, and bacterial contamination found in cows' milk. Physical and psychological benefits of breastfeeding for the mother as well as psychological, immunological, and anti-allergenic benefits of breastfeeding for the infant are discussed; the benefits of bottle feeding are presented briefly. The composition of formula is discussed and guidelines for choosing a formula are offered. Information is presented on ways to minimize contaminants in the diet and recommendations for government action are offered. Appendices include information on: (1) pesticides in human milk, (2) pesticides in cows' milk, (3) filtration of drinking water, (4) approximate analyses of commonly used infant formulas compared to human and cows' milk, and (5) testing milk for contaminants. A 20-item glossary is also included. (JMB)