This thesis is an investigation of marketing messages and their impact on the decisions made towards health behaviours. The objective of this study was to measure the persuasiveness of negatively versus positively phrased health messages. We measured the effects of goal and attribute framing, along with issue involvement, on choice to obtain the HPV vaccination. Female participants were tested on their level of involvement with the topic of STD's and read either a gain-framed or a loss-framed HPV vaccination message. Twelve choice sets with six vaccination attributes, two of which were framed, were presented and choice was measured using a discrete choice experiment. Results of this study indicate an interaction effect between high involvement participants exposed to a loss-framed message. Gain-framed attributes were also significant on choice. Contributions from this study suggest that when targeting high involvement groups, negatively-framed messages and positively-framed attributes are most effective in changing health-related behaviours.