Because of its multiracial character, Hawaii presents a unique opportunity to carry out demographic investigations of the etiology of certain common cancers. Tumors with substantially different incidence rates among the major ethnic groups in the Islands, or between a given immigrant group and its country of origin, are of particular interest for such studies. Among the cancer sites meeting these criteria, nasopharynx, stomach, prostate, large bowel, liver, female breast, uterine corpus, ovary, bladder, and thyroid are particularly prominent.