Viruses are efficient carriers of genetic material between cells. They specifically recognise a target cell and utilise host functions for genome delivery to the replication site. A mature viral capsid emerging from an infected cell serves at least three distinct functions. It enables virus egress from the infected cell, protects the extracellular genome against chemical and physical stress and mediates virus entry into a non-infected cell. How can a virus particle be stably assembled in an infected cell and moments later-after passing through the extracellular milieu-be disintegrated by a non-infected cell? In this review I discuss how adenovirus, a DNA virus, recruits cellular and viral factors and makes use of its own cysteine protease to regulate capsid assembly and disassembly. Copyright 1998 John Wiley & Sons, Ltd.