Nasopharyngeal carcinoma (NPC) has been reported to occur in Alsaka Natives (Eskimos, Indians, and Aleuts) at a rate greater than 15 times the rate for U.S. whites. At least 3 cases of NPC have occurred in close relatives of a Northern Alaskan Eskimo family. All 3 patients had poorly differentiated tumors and have died. Blood groups, HLA antigens, and antibodies to Epstein-Barr virus (EBV) were studied in the family members. EBV titers were elevated in the 1 NPC patient tested and in 1 of 15 other family members tested. All family members studied except 1 were of blood group A, Rh-positive, and HLA types AW24, CW3, CW40/A2, CW2 and B27. This was the first report of more than 2 cases of NPC in a single family in the United States.