This is the second edition of the TI Defence and Security Programme's Handbook, Building Integrity and Reducing Corruption in Defence and Security: 20 Practical Reforms. This Handbook has a simple purpose: to show busy decision makers how significant progress can be made in tackling corruption risks in defence and security. In it, we recommend ways to diagnose corruption risks and how to lead change in defence and security establishments.  We discuss military operations, the procurement process, and budgets and assets, and show how nations are tackling corruption risks in each of these.  This edition of the handbook came about in response to the positive reaction to the first edition, and draws upon lessons we have learned in the past three years of our work.  People from some 35 nations have contributed to the ideas and approaches described here.