By offering various pelleted diet modifications to five species of Callitrichidae, a palatable 24% protein diet was developed. The animals received limited fruit supplement, and families received an additional meal of commercial baby food. The pellets supplied approximately 75% of dietary energy and 95% of total protein. In 15 months on this regimen, mortality dropped drastically and fertility improved. No signs of a nutritional deficiency were observed. It was concluded that the nutrient levels of this diet were adequate or above actual requirements.