This article presents a control flow analysis methodology based on UML 2.0 sequence diagrams (SD). In contrast to the conventional code-based control flow analysis techniques, this technique can be used earlier in software development life cycle, when the UML design model of a system becomes available. Among many applications, this technique can be used in SD-based test techniques, model comprehension and model execution in the context of MDA. Based on the well-defined UML 2.0 activity diagrams, we propose an extended activity diagram metamodel, referred to as Concurrent Control Flow Graph (CCFG), to support control flow analysis of UML 2.0 sequence diagrams. Our strategy in this article is to define an OCL-based mapping in a formal and verifiable form as consistency rules between a SD and a CCFG, so as to ensure the completeness of the rules and the CCFG metamodel with respect to our control flow analysis purpose and enable their verification. Completeness here means if the CCFG metamodel has all classes and associations needed, and the rules are adequate with respect to our purpose. Furthermore, we define Concurrent Control Flow Paths, which are a generalization of the conventional Control Flow Path concept. The control flow analysis technique is applied to an example SD to demonstrate the feasibility of the approach.