In this article, grade integrity is defined as to the extent to which each grade awarded, either at the conclusion of a course or module of study or for an extended response to an assessment task, is strictly commensurate with the quality, breadth and depth of a students' performance. The three basic requirements for this aspiration to be realised are, in order: assessment evidence of a logically legitimate type; evidence of sufficient scope and soundness to allow for a strong inference to be drawn; and a grading principle that is theoretically appropriate for coding the level of a student's performance. When further developed, the general approach outlined could produce positive side benefits, including ways of dealing with grade inflation.