This paper examines annual changes in the participation of developing countries in three kinds of learning assessment activity over the past three decades. It specifically highlights, and provides initial explanations for, the worldwide spread of national and regional assessments since the mid-1990s. The paper argues that national learning assessments--namely, non-standardised, context-sensitive and non-comparable learning assessments--have become a preferred tool of educational policy makers in developing countries. The increasing demand by educational stakeholders for accountability and the relative advantages of national assessments are likely to amplify this trend in the future. Patterns of country participation will further depend on the policies of international agencies, NGOs and regional associations that support and advise countries on learning assessments. (Contains 4 notes, 4 tables, and 4 figures.)