Pre-testing messages with audience members is a critical step in the creation of effective health information. Quantitative methods for message testing have limited effectiveness, as they cannot reveal complications with language and comprehension. Cognitive response testing (CRT), a form of qualitative research, allows the interviewer to probe for deeper understanding of comprehension and language by asking participants to paraphrase items, discuss thoughts or emotions that come to mind and offer suggestions for improvement. This study explores the usefulness of CRT in message development and testing, adding to the literature regarding qualitative methods in public health. CRT was employed to evaluate health messages on two topics—bioterrorism and influenza vaccination. This technique effectively identified message terminology and concepts that respondents found unfamiliar or confusing, providing the framework needed for message revision. Commonly misunderstood words were replaced and confusing concepts were explained in the revised messages, making pre-tested messages more likely to be appropriate for the intended audience. These findings are consistent with previous research that establishes the usefulness of CRT in the evaluation and development of health-related messages and surveys.