We will recruit 12 Hispanic prepubertal children with CF (ages 7-12, Tanner I) and 12 Hispanic adolescents (ages 15-17, Tanner 3 or 4) from the CF Centers at University of Texas Southwestern and Baylor College of Medicine in Houston. Information obtained from these subjects will be compared to 12 prepubertal and 12 adolescent Caucasian children with CF recruited from the same CF centers. We will categorize the subjects according to glucose tolerance (OGTT), as well as insulin secretion and insulin sensitivity using the IVGTT and the Minimal Model, as modified for children. We will also compare the historical information of socio-economic status and family history. Clinical status will be characterized by measuring pulmonary function and modified NIH scores, in addition to measuring levels of circulating cytokines. Gluconeogenesis (GNG) will be quantified by measuring the incorporation 2H into the 2nd, 5th and 6th carbons of glucose. Whole body protein turnover (WBPT) will be measured using [1-13C]leucine. Nutritional status will be determined by three-day food journals, and intake will be compared to energy needs, utilizing indirect calorimetry to measure resting energy expenditure. Subjects will be recruited from the CF centers at the University of Texas- Southwestern and the South Central CF Consortium.