Zinc balance was studied during the last trimester of pregnancy in four teenagers. Diets composed of natural foods and mineral salts contained 10.5, 15.0 and 19.5 g nitrogen, and 26, 29 and 32 mg zinc. Urinary zinc was 2 % of daily total excretion and was relatively constant for a given subject. Dermal losses were larger than anticipated, 2.8 mg/day, and constituted about 11 % of daily zinc loss. Fecal zinc was 87 % of total daily loss, and varied within subjects and treatment groups. The magnitude of fecal zinc loss was dependent on the volume of fecal dry solids passed and zinc content of dry fecal material was remarkably constant within subjects and treatment groups. Balance for all subject-treatments was about 4 mg/day.