Lower incidence rates of cancer for all anatomic sites combined were found in male and female Spanish-surnamed residents of Los Angeles County when compared to other whites. These Mexican-Americans were at lower risk for cancer of the buccal cavity, colon, rectum, larynx, lung, breast, bladder, prostate, and testis, and were at higher risk for cancer of the stomach, gallbladder, liver, and cervix. Immigrant Mexican-Americans had incidence rates most divergent from other whites, whereas indigenous Mexican-Americans had rates between the other two groups. The cancer pattern in Mexican-Americans was generally similar to that in American Indians. These data were most consistent with environmental variations in cause.