ABSTRACT: The use of a well-defined process is a widely recognized approach to increasing quality and productivity in software development. Building software processes from scratch each time is expensive and risky. Therefore, they are often created by tailoring existing processes and standards. Process tailoring is a knowledge-intensive activity. This research explores the link between knowledge support and software process tailoring performance under different levels of tailoring task complexity. It theoretically develops and tests how the fit between knowledge (generalized and contextualized) and software tailoring task complexity influences process tailoring performance. Process tailoring performance is conceptualized in terms of effectiveness and efficiency. The results from an experiment and a protocol analysis show that contextualized knowledge outperforms generalized knowledge in improving tailoring performance, and that such improvement in performance is greater in complex process tailoring tasks when compared to simple tasks.