Examinations were made of 302 full-term newborn infants with severe jaundice (indirect bilirubin >20 mg./100 ml. in 79.7% of the cases) for G6PD deficiency by 3 diagnostic methods, of which the methaemoglobin-elution test proved to be superior. 99 or 32.7% of the cases were found to be G6PD deficient by the latter method (59 males and 40 females): a male : female ratio of 1.47. 8 of the 59 males had normal values of G6PD activity and are probably cases of the mild G6PD deficiency type. The difficulties involved in the diagnosis of G6PD deficiency in the newborn period were discussed
