Objectives: Impaired longitudinal growth and poor weight gain are common and important problems in children with cystic fibrosis. This study evaluates the hypothesis that adjunctive growth hormone (GH) therapy augments the growth response to nutritional supplementation. Study design: We recruited 18 prepubertal children who received enteral nutritional supplementation for at least 2 years before enrollment. Nine were randomly assigned to receive no GH for 1 year, followed by 1 year of GH. Nine were randomly assigned to receive 1 year of GH followed by a second year of GH. Measurements included height, weight, pulmonary function, lean tissue mass, bone mineral content, hospitalizations, outpatient antibiotic use, and caloric intake. Results: Growth hormone resulted in significant improvement in height, weight, bone mineral content, lean tissue mass, and number of hospitalizations. Pulmonary function was similar at baseline. Absolute forced vital capacity and forced expiratory volume in 1 minute significantly increased in GH treatment, but there was no significant change in percent predicted pulmonary function. Caloric intake was similar in both groups during both years. Conclusions: These results suggest that GH is a useful for enhancing growth in children with cystic fibrosis receiving enteral nutritional supplementation.