This paper examined ethnic and socioeconomic differences and incidence trends for 18 adult cancers in New Zealand between 1981–2004, with 47.5 million person-years of follow-up. Compared to European/Other people in New Zealand, Māori and Pacific people are 1.5–2.5 times more likely to develop cervical, endometrial, stomach and pancreatic cancers; Māori, Pacific and Asian people are 5 times more likely to develop liver cancer. For European/Other, rates of colorectal, bladder and brain cancers were 1.5–2 times higher and melanoma rates 5–10 times higher than rates of other groups; Pacific and Asian kidney cancer rates were half those of Māori and European/Other. Trends over time revealed faster decreases in rates of cervical cancer in Māori and Pacific people, whereas and Māori rates of colorectal and breast cancer increased faster, than European/Other rates. Male lung cancer rates decreased for European/Other, were stable for Māori and increased for Pacific. Female lung cancer rates increased for all ethnic groups. Other than lung (rate ratio 1.35 men, 1.56 women), cervical (1.35) and stomach cancer (1.23), differences in incidence by income were modest or absent.
