The rationale for, and experience with, the use of assessment to improve the quality of education in African education systems over the past two decades are described for four categories of assessment: (i) public examinations, (ii) national assessments; (iii) international assessments, and (iv) classroom assessment. The case for reform of public examinations is based, first, on a perception that their quality is poor in many countries and, secondly, on the belief that since teachers align their teaching to the demands of examinations, improving them will effect change in what teachers teach and, as a consequence, in the quality of students’ learning. Examples of the use of examination data to improve student achievements are provided. Evidence is considered relating to the effects of changes in examinations on the content of teaching, level of student achievements, and students’ cognitive processing skills. National assessment activity spread through the whole of Africa during the 1990s. Although information derived from national assessments is obtained from individual students (chosen to represent all students at a particular grade in the education system), data are aggregated to provide an assessment of the education system. The primary purpose of such an assessment is to describe how well students (and identifiable subgroups of students) are learning. To date, use of information derived from assessments seems limited for the most part to government commissions, reviews, and education reform programs in a number of countries. International assessments, which share many procedural features with national assessments, provide comparative data on achievement in more than one country. Few African countries have participated in them. However, some of the national assessments that have been carried out allow international comparisons. Although classroom assessment has attracted the least attention in proposals to use assessment to improve the quality of education, it is likely to have a greater impact on student learning than any other form of assessment. Advantages and disadvantages of school-based assessment in contributing to grades in public examinations (a feature of examinations in some countries) are considered. Proposals to improve public examinations, national assessments, and classroom assessment are presented. Factors that may inhibit the use of assessment to improve the quality of education are described.