This thesis provides an historical comparison of the ethnic questions in the censuses of Canada and New Zealand. The comparison spans six census years, selected to provide the best examples of changes in the respective censuses since World War II. Certain critical aspects are examined in detail, including the question wording, response categories, helpnotes, selected coding procedures, and multiple responses. Research material for this thesis was obtained from published and unpublished material from both Statistics Canada and Statistics New Zealand. Sociological definitions and theory relating to ethnicity are investigated, and these issues are related back to the difficulties in developing an ethnic question for Censuses. The 'race' component of census ethnic data is noted, and the possible explanation of the 'census as fossil' is offered. The tensions between the visibility of the ethnic question and the invisibility of ethnic classification systems are also explored. Censuses of Population, and especially the ethnic questions in censuses, are developed by official statisticians in the context of contemporary cultural norms and values. To that end, the economic and social histories of Canada and New Zealand are reviewed to provide a background for the discussion of each ethnic question. Where pertinent the comparison includes Australia, United Kingdom and the United states. The main differences between New Zealand and Canada are found to be in population composition (differences in the indigenous population, as well as the anomaly of the French in Canada) and the legislative requirements for ethnic data. The differences in the ethnic census data are discussed in this context, especially the fact that the New Zeeland question is a cultural affiliation measure, whereas the Canadian 'ethno-cultural' questions relate to ancestry, race and visible minority status. All census data are reliant on the goodwill of the public. If census ethnic data are to remain credible, official statisticians must continue to seek to understand the meaning and impact of census ethnicity questions, and must develop ways of collecting and disseminating the data that satisfy the needs of the users, producers and suppliers of the data. This thesis seeks to contribute to this endeavour.