This case study explores the assessment of students’ learning outcomes in a second-year lecture course in biosciences. The aim is to deeply explore the teacher’s and the students’ experiences of the validity and reliability of assessment and to compare those perspectives. The data were collected through stimulated recall interviews. The results showed that grades did not always reflect the learning outcomes and that the intended level of understanding was not always measured. In addition, the teacher and the students thought that the assessment criteria were unclear, which in turn led to the unreliability of the assessment. These problems with the validity and reliability of assessment led to perceptions that the assessment was unfair. The results imply that grades should be critically evaluated as indicators of the quality of learning outcomes. In addition, practical implications are discussed.