Serum gamma-glutamyl transferase (GGT) activities were determined on the third day of life in healthy controls (n:15) and in infants with non-hemolytic hyperbilirubinemia (n:16). GGT activities were 39.6 +/- 28.4 units/ml and 46.6 +/- 26.7 units/ml, respectively. There was no statistical difference between both groups (p greater than 0.05).