Introduction The ethnic distribution in mortality rates for New Zealand (NZ) military personnel in World War I has never been described.

Methods Mortality data for military personnel in the NZ Expeditionary Forces (NZEF) were obtained from an electronic dataset (Roll-of-Honour) covering all deaths in these personnel during World War I and the immediate post-war period (1914–1923). All NZEF were allocated (using a classification system based on names and background) into the following ethnic groups: European/Other, Māori (indigenous New Zealanders) and Pacific peoples.

Results The highest all-cause mortality (deaths from enemy action, wounds, disease, and other) was experienced by Māori personnel. The majority of deaths among European/Other and Māori personnel were a result of being killed in action. Pacific personnel experienced the lowest all-cause mortality rate. Mortality rates from disease varied greatly by ethnic group, with Māori and Pacific personnel both experiencing higher rates than European/Other personnel. When deaths from the 1918 to 1919 influenza pandemic are excluded from the analysis, Māori and Pacific personnel still had significantly higher mortality rates from disease compared to European/Other personnel (rate ratio 3.92, 95% CI 3.14 to 4.91 and rate ratio 3.45, 95% CI 2.42 to 4.91).

Conclusions We document for the first time higher all-cause mortality burden among Māori compared with European/Other for NZ's World War I effort. Also identified was the large variation in disease mortality, with Māori and Pacific personnel suffering to a disproportionately greater extent. These historical results serve as a reminder that tackling health inequalities is a long-term commitment that requires ongoing public health attention.