The early twenty-first century has witnessed a drive to establish national ID card systems in many countries. While some ID documents have existed for centuries, and have always been surveillant, new ones depend on electronic databases and, often on biometrics. This rachets-up exponentially their surveillance power, not least because the new systems also offer links with other databases than national registries. But even when these systems are presented as technical upgrades, they are not merely a technical matter. New IDs have a pre-history, are promoted by high-tech corporations and have new consequences for social sorting and for the exclusion of certain groups. Careful analysis of ID cards as surveillance shows how conventional assumptions about state-and-citizen need rethinking if just and fair systems of identification are to be developed.