Clinical trials are fundamental to the advancement of medicine but constantly face recruitment difficulties. Various clinical trial search engines have been designed to help health consumers identify trials for which they may be eligible. Unfortunately, knowledge of the usefulness and usability of their designs remains scarce. In this study, we used mixed methods, including time-motion analysis, think-aloud protocol, and survey, to evaluate five popular clinical trial search engines with 11 users. Differences in user preferences and time spent on each system were observed and correlated with user characteristics. In general, searching for applicable trials using these systems is a cognitively demanding task. Our results show that user perceptions of these systems are multifactorial. The survey indicated eTACTS being the generally preferred system, but this finding did not persist among all mixed methods. This study confirms the value of mixed-methods for a comprehensive system evaluation. Future system designers must be aware that different users groups expect different functionalities.