Supplementary feeding programs are common in developing countries. These programs often cannot demonstrate an impact on child growth, however, possibly because they tend to reach older children. This study examines the impact of nutritional supplementation on annual growth rates in length and weight from birth to 7 y of age in 1208 rural Guatemalan children. A series of multiple linear regression models is used to control for initial body size, diarrheal disease, home diet, socioeconomic status and gender. During the first year of life, each 100 kcal/d (418 kJ) of supplement was associated with approximately 9 mm in additional length gain and 350 g in additional weight gain; the benefit decreased to approximately 5 mm in length gain and 250 g in weight gain during the 2nd y of life. Between 24 and 36 mo of age, supplement only had a significant impact on length. There was no impact of nutritional supplementation on growth between 3 and 7 y of age. Patterns were the same if supplement intakes were expressed as a percent of recommended allowances or growth was expressed as a percent of the expected rate. These impacts of nutritional supplementation on growth coincide with the ages when growth velocities, as well as growth deficits, are greatest in this population.