Abstract: Traditional worst-case execution-time analysis (WCET analysis) computes upper bounds for the execution times of code. This analysis uses knowledge about the execution context of the code and about the target architecture. In contrast, the WCET analysis for reusable and portable code has to abstract from parameters that are unknown until the code is finally used. The analysis is done in two steps. The first step computes abstract WCET information to support the reuse and portability of the WCET information. The second step uses the abstract WCET information to compute concrete WCET bounds when the application context and the timing parameters of the target system are known. The paper describes each of the two analysis steps. It demonstrates how WCET information can be made portable and reusable.