Agile development methodologies are gaining acceptance in the software industry. If they are to be used for constructing securitycritical solutions, what do we do about assurance? This paper examines how conventional security assurance suits agile methodologies for developing software-intensive systems. It classifies security assurance methods and techniques with regards to their clash with agile development. Suggestions are made for alleviating mismatches between these two methods.. Categories and Subject Descriptors K.6.5 [Management of Computing and Information Systems]: Security and protection. D.2.4 [Software Engineering]: Software/program verification. K.6.1 [Management of Computing and Information Systems]: Project and people management — lifecycle. K 6.3 [Software Engineering]: Software management – software process. General Terms Management, Documentation, Security. Keywords Agile methods, security, assurance, security assurance, security engineering, software development...