This paper will introduce the IEA International Computer and Information Literacy study (ICILS 2013); the first international comparative study of ICT literacy and digital competencies among school students. At present, 12 European countries are planning to participate with support from the European Commission. In this study Computer and Information Literacy (CIL) has been defined as the ability to use computers to investigate, create and communicate in order to participate effectively at home, at school, in the workplace and in the community (Fraillon & Ainley, 2010). ICILS will explore differences across countries in CIL achievement in Grade 8 students and personal and educational factors that may contribute to variation in CIL achievement. ICILS will also investigate the influence of students’ backgrounds (including gender, socio-economic background, and language background), access to and confidence in using computer technologies on student CIL, and variations among countries in those influences. This paper will provide a discussion of the design and implementation of ICILS with a focus on maintaining relevance and equivalence across the range of participating countries. Topics covered in the paper will include: the nature of the CIL construct; the computer-based assessment design; and the concepts underpinning the questionnaire materials.