This study was aimed at the comparison of values of anti-Epstein-Barr virus serology in different groups of patients suffering from carcinoma of the nasopharynx (NPC), classified according to histological type defined by the new classification of the WHO. A group of patients with other tumours of the upper respiratory and digestive tract was used as a control. Antibody levels were high in patients with undifferentiated carcinomas whilst they were low in the controls. In patients with differentiated carcinomas antibody levels were most often equivalent to those of the controls, even though high values were sometimes seen. These findings would appear to offer evidence that the new histological classification of NPC is well founded, and to a certain extent reflect the epidemiological, clinical and therapeutic classifications already seen for these two types of carcinoma.