The Progress in International Reading Literacy Study (PIRLS) is a five-yearly international study of reading attainment of Primary 4 students in different countries and regions, and investigates how it is related to their reading experiences at home and in schools. The study deploys both reading assessment tasks and questionnaires to provide a holistic picture of students’ reading literacy development. Hong Kong, a region that has initiated “Reading to Learn” as one of the four key tasks in nurturing students’ capability of “Learning to Learn” in the curriculum, has participated in several cycles of PIRLS study since 2001. Results to date have offered multifold implications to teachers, schools and parents to optimize pedagogy and literacy environment, and to policymakers for monitoring and evaluating the on-going curriculum reform.