In Liaoning Province in northeastern China, we found a G6PD-deficient patient at the age of 3. By the classification of the World Health Organization, this patient was categorized as class I (very severe G6PD deficiency). When we investigated the G6PD gene of the patient, we found that he had a replacement of G to A at nucleotide 1339. As a result, the amino acid at position 447 should change from Gly to Arg. This replacement is known as G6PD Santiago de Cuba, because it was first discovered in a Cuban boy who showed heavy chronic anemia. Today, 28 G6PD variants have been reported in the Chinese population, and all are categorized as class II (severe deficiency) or class III (mild deficiency); in class II or III deficiency, anemia is not present in daily life, but hemolytic attack can occur when the carrier ingests certain oxidative medicines or foods. This is the first report of a G6PD-deficient Chinese patient in the category of class I. We intended to find other G6PD-deficient cases in northeastern China and tested several hundred blood samples, but no cases of G6PD deficiency were found (0/414). In central China, where falciparum malaria was endemic from the 1950s to 1970s, we found two G6PD-deficient cases (2/27) and the other members from their families whose variant type was G6PD Kaiping (1388G > T), which is a common variant in the Chinese population.