The study of persuasive health messages—their design, dissemination, and impact—is ubiquitous in the communication discipline. Words, sounds, and images—alone or in combination—can move people to change their minds and their bodies. Micro-level topics surround questions of message content (argumentation scheme, evidence, qualifying language, and figurative language), structure (message sidedness, standpoint articulation, inoculation, and sequential strategies), and format (channel and audiovisual effects). Macro-level topics in this area include message sensation value, narrative, framing, emotional appeals, and tailoring. Central theoretical frameworks used to guide message design research, include health behavior change theories, information processing theories, and theories/frameworks for message design. In addition, some of the methodoligical issues inherent in message design research are questions of analysis, validity, and measurement. Four streams of past scholarship that inform persuasive health message design research: Greek rhetoric, mass communication research begun during World War II, the development of health communication as a research focus within the communication discipline, and the development of computer and telecommunications technology. Directions and challenges for future research include the need for a clear, coherent, and comprehensive taxonomy to classify message characteristics and attention to several methodological issues.