This study utilized responses from Taiwanese preservice elementary teachers to describe and analyze their conceptions about the assessment of science learning and the extent that these conceptions were coherent with their views of learning science. A methodological framework of phenomenography was used for the study. The results revealed that the preservice teachers' mode of assessment was coherent with a traditional view of learning but their performance mode of assessment was not well developed. Improving preservice teachers' conception of assessment requires clarifying and reconstructing their conceptions of and coherence between assessment, curriculum, pedagogy, and learning. (Contains 1 figure.)