Salicylamide glucuronide formation has been studied in 23 newborn babies with erythrocyte G-6-PD deficiency and in 15 normal newborns on the first day of life. Glucuronide formation was significantly lower (p < 0.001) in the former in comparison with the controls. In the newborns with G-6-PD deficiency who subsequently became hyperbilirubinemic an even lower mean glucuronide formation was observed (p < 0.01) in respect to the non-jaundiced G-6-PD-deficient newborns.