Secure Tropos is an extension of Tropos methodology, which considers security throughout the whole development process. The main concept of Secure Tropos is the security constraint that captures constraints regarding security. Similarly, the concepts of dependency, goal, task, resource, and capability were also extended with security in mind. In this paper, the authors present the SecTro tool, a CASE tool that guides and supports the developers in the construction of the appropriate models of Secure Tropos.