This paper reviews current known issues in student self-assessment (SSA) and identifies five topics that need further research: (1) SSA typologies, (2) accuracy, (3) role of expertise, (4) SSA and teacher/curricular expectations, and (5) effects of SSA for different students. Five SSA typologies were identified showing that there are different conceptions on the SSA components but the field still uses SSA quite uniformly. A significant amount of research has been devoted to SSA accuracy, and there is a great deal we know about it. Factors that influence accuracy and implications for teaching are examined, with consideration that students' expertise on the task at hand might be an important prerequisite for accurate self-assessment. Additionally, the idea that SSA should also consider the students' expectations about their learning is reflected upon. Finally, we explored how SSA works for different types of students and the challenges of helping lower performers. This paper sheds light on SSA research needs to address the known unknowns in this field.