TUBOUND is a conceptually new tool for the worst-case execution time (WCET) analysis of programs. A distinctive feature of TUBOUND is the seamless integration of a WCET analysis component and of a compiler in a uniform tool. TUBOUND enables the programmer to provide hints improving the precision of the WCET computation on the high-level program source code, while preserving the advantages of using an optimizing compiler and the accuracy of a WCET analysis performed on the low-level machine code. This way, TUBOUND ideally serves the needs of both the programmer WCET analysis by providing them the interface on the very abstraction level that is most appropriate and convenient to them. In this paper we present the system architecture of TUBOUND, discuss the internal work-flow of the tool, and report on first measurements using benchmarks from M