This study empirically evaluates Hale and Haworth's cognitive processes model for programmers engaged in software debugging. They claim that across all levels of experience, software programmers engage in the same activities and follow a similar pattern of activities directed by search strategies. Verbal protocol analysis of data gathered during a staged problem‐solving episode (e.g., fixing a hidden bug) was used to evaluate Hale and Haworth's hypothesized debugging tasks, as well as the hypothesized sequence in which the tasks are performed. Empirical support for Hale and Haworth's model was strong. Specifically, the set of hypothesized debugging tasks is both accurate and complete. Further, the model effectively represents the process by which programmers generate and evaluate hypotheses, and the manner in which programmers recursively attack a debugging problem. Unsupported are those complex debugging sequences involving multiple possible paths. This study extends the understanding of the mechanisms by which programmers choose, implement and evaluate debugging rules and strategies. Results verify that all observed programmers utilize a pattern of cognitive process steps as well as comprehension strategies to derive needed declarative knowledge. The results support a goal‐driven model of program debuggers' cognitive processes depicting a hierarchy of levels with an inherent control structure that directs debugging process steps. Copyright © 1999 John Wiley & Sons, Ltd.