Assessment of students in the learning process may have several reasons (knowledge assessment, ranking etc.). One reason presented in this article would be to use the assessment as a way to enhance learning. At Stockholm University Library, PhD-students in Chemistry annually partake in a library course, where they have to write a mandatory essay and, from 2012, review a fellow student’s essay. Comparing and discussing the former and the new ways of assessing, this article aims to discuss assessment as a way to enhance learning.