The relation between nasoenteric formula caloric infusion rate and the serum bilirubin level was examined in 15 healthy subjects. The study protocol spanned 3 days and included fasting studies on day 1, continuous maintenance nasogasteric feeding of a formula diet on day 2, and continuous feeding at a rate twice the maintenance level on day 3. Blood studies were performed in the early morning of each day. Fifteen subjects underwent the fasting measurements and the maintenance infusion, while 11 underwent all 3 days of the protocol. With the maintenance infusion serum bilirubin fell from the fasting value of (X ± SD) 0.77 ± 0.53 to 0.63 ± 0.49 mg/dl for a reduction of 18% (p < 0.05). For the subgroup of 11 subjects receiving two levels of formula infusion, fasting and maintenance serum bilirubin levels were 0.81 ± 0.57 and 0.65 ± 0.47 mg/dl, respectively, (p < 0.05). With the twice maintenance infusion the plasma bilirubin decreased further to 0.46 ± 0.29 mg/dl, a decrement of 43% relative to fasting (p < 0.01). No other significant changes were detected during the protocol in the standard blood chemical and hematologic studies. Thus, the serum level of bilirubin is inversely related to the formula caloric infusion rate during continuous nasoenteric feeding.