Teachers' conceptions of assessment can be understood in terms of their agreement or disagreement with four purposes to which assessment may be put, specifically, (a) improvement of teaching and learning, (b) school accountability, (c) student accountability, or (d) treating assessment as irrelevant. A 50-item Teachers' Conceptions of Assessment (COA-III) questionnaire was completed by New Zealand primary school teachers and managers ( n =525). The COA-III, based on the four main purpose-defined conceptions of assessment, was analysed with structural equation modelling and showed a close fit of the data to a hierarchical, multi-dimensional model (2 =3217.68; df =1162; RMSEA=.058; TLI=.967). On average, participants agreed with the improvement conceptions and the school accountability conception, while rejecting the view that assessment was irrelevant. However, respondents disagreed that assessment was for student accountability. Improvement, school, and student accountability conceptions were positively correlated. The irrelevance conception was inversely related to the improvement conception and not related to the system accountability conception. Surprisingly, no statistically significant differences were found in mean scale scores for each conception regardless of teacher (age, gender, role, assessment training, or assessment practices) or school (size, location, or socio-economic status) variables. Implications for the use of the COA-III for policy implementation and teacher professional development are discussed.