Assessment of nutritional status of patients with cystic fibrosis of the pancreas (CFP) showed that poor growth was associated with low concentrations of albumin, urea nitrogen, and cholesterol in serum and with elevated white blood cell (WBC) counts. Patients with CFP maintained weight approximately 1 standard deviation below the mean until 8 years, after which there was a progressive decline in growth rate compared to normal. A complete dietary supplement consisting of a beef serum hydrolysate, a glucose polymer, and medium-chain triglycerides was given to 15 patients for a year. Patients who received the diet showed significant gains in weight, significant increase in clinical score, significant increase in serum albumin level, and a significant drop in the WBC count compared to control patients who did not receive the supplement.