Background A process map is a diagram showing the sequential steps and decisions used to accomplish a procedure from start to finish. Process maps are a standard tool in continuous improvement efforts. They have not been used routinely in clinical trials although they are well suited to display trial processes. Purpose We present the use of process maps as a tool to visualize and to monitor the correctness of trial work flows. We show that process maps can be used to assure that trial processes are conducted according to the SOP. Methods We describe how a process map is made. We then derive process maps from two sources: the SOP and trial procedures as currently implemented. We compare these maps to each other, using the SOP maps as the gold standard, to check that work is done according to the written procedures. Results Eight process maps were produced from each source. 172 differences were found between the SOP maps and the walkthrough maps. Differences included the addition of extra steps, order errors, step mistakes, and ambiguities. Limitations These process maps focused only on clinic procedures, so interactions with other trial components were not considered. The maps were made after the trial started, which may have biased their content and use. Conclusion Process maps are a simple tool to check if clinical trial processes are operating as designed and offer an effective means to identify and correct such divergences. Further research should focus on using process maps in the design phase of trials, analyzing the cost to benefit ratio for process maps, and linking the analysis of the process map to monitor queries to quantify the improvement gained from using this technique. Clinical Trials 2009;6:373-377.http://ctj.sagepub.com