Growth failure and malnutrition are common clinical features in Alagille syndrome. The purpose of the study is descriptive in nature to identify whether development of pancreatic insufficiency contributes to malaborption, failure to thrive and presumed energy imbalance that are seen in children with AGS. We hypothesize that pancreatic dysfunction may contribute to the malaborption leading to altered bone density and growth delay commonly observed in children with AGS. This is a twelve-month study where subjects are evaluated on three occasions. At baseline and twelve-month visits, the subject will spend one night in the Clinical Research Center. The six-month visit will be an outpatient visit. During the baseline visit the following procedures will be done: anthropometry, REE, DEXA, TOBEC, bone age, direct pancreatic function test. The following labs will be drawn: hepatic function test, prealbumin, cholesterol, comprehensive metabolic panel, immunoreactive trypsinogen, Vitamin E and PT/PTT. Serum and urine from each child will be saved. After each visit three day diet record and 72 hour stool collection were requested. Stool will be analyzed for fecal fat, fecal nitrogen and fecal elastate, a sensitive and noninvasive marker of pancreatic function. The six month visit consists of anthropmetry and DEXA and another three day diet record and stool collection. At the 12-month visit all of the procedures (except for the direct pancreatic stimulation test) that were performed at the baseline visit will be done.