In the ongoing programmes to develop indicators of education systems, the measurement and presentation of education outcomes is one of the primary goals. This holds for national as well as for international programmes. However, to date the choice in available outcome indicators typically has been rather small. Researchers and policy makers have relied mainly on achievement measures in reading, mathematics or science, which have an internationally recognised level of quality. Nevertheless students learn more subjects than these three, and much of what they learn in school is not taught explicitly in one subject or another. Indicator and assessment programmes have begun to focus on competencies of a more cross-curricular nature. This chapter describes how and why cross-curricular competencies came to the forefront of international assessment development work, the present state of this development work and pertinent issues for continued development.