This paper advances a model describing how peer assessment supports self-assessment. Although prior research demonstrates that peer assessment promotes self-assessment, the connection between these two activities is underspecified. This model, the assessment cycle, draws from theories of self-assessment to elaborate how learning takes place through peer assessment. The model is applied to three activity structures described in the literature to analyse their potential to support learning by promoting self-assessment. Broadly speaking, the model can be used to understand learning that takes place in a variety of peer assessment activities: marking/grading, analysis, feedback, conferencing and revision. This approach contrasts most studies on peer assessment, which have focused on calibration of instructor and peer grades, rather than learning opportunities.