The Health Belief Model provides a framework to understand motivators for volunteering for medical research. Motivators can take the form of social and personal benefits. In this systematic review of review articles, we contrast motivators of participation in actual cancer trials to those in actual HIV vaccine trials. We retrieved eight review articles from 2000 to 2012 examining motivators to participation in actual cancer trials. Personal benefits were most often psychological in nature, such as "coping with symptoms." Social benefits included "advancing research," "helping other cancer patients," and "for their family." While specific motivators vary between considerations - cancer research and HIV vaccine trials, these motivators fall into similar categories at similar frequencies. For example, personal/psychological benefits are common in each. Participant recruitment must be mindful of these categories of motivators for both cancer and HIV vaccine research.