Introduction: Breast-milk fortifiers, recommended for premature infants, are seldom available in developing countries. We describe the characteristics of growth in exclusively breast-fed pre-term infants under ambulatory Kangaroo Mother Care (KMC), supplemented with formula when necessary, and the relations between growth and the composition of premature breast milk, the nutritional status of the mother and the infant’s condition at birth. Methods: Design: Prospective cohort study. Setting: Neonatal Unit at Clínica San Pedro Claver and the Kangaroo Mother Care (KMC) programme, an ambulatory clinic from the Clínica del Niño, tertiary care clinics in Bogotá, Colombia. Subjects: 115 mothers and their 129 healthy, pre-term infants; 126 infants (98.4%) were available for evaluation at term. Interventions: The weights of the infants were monitored daily until they achieved 15 g/kg per day for 2 days, and then weekly until term. Formula was offered to infants who were not thriving. The composition of fore and hind milk was measured weekly, and clinical chemical variables of both mothers and infants were measured at entry into the programme and at term. Results: Sixty infants (47.6%) did not require supplementation, and in 14 of those who needed supplement, adequate weight gain before reaching term was achieved and supplement could be stopped. The infants that received supplementation throughout had lower growth indices. Growth and need for supplementation were not related to breast-milk composition. Conclusion: The growth indices at term were close to those expected for term infants born in Bogotá. Our strategy thus appears to be a reasonable alternative for feeding pre-term infants within an ambulatory KMC programme. It is a rational, ethical alternative that should be explored in other settings.