This paper discusses a method to compare progress in reading achievement across countries. The method uses measures of achievement in primary schools from PIRLS and compares them to secondary school results from PISA. Results describe an interval in which estimates of progress can lie, depending on the comparability of these two assessments. Progress estimates are also adjusted for age, gender and other characteristics that differ between countries and surveys. The paper also demonstrates how useful these estimates are for policy analysis by comparing achievement progress across early and late tracking countries.