This dissertation examined the persuasive effects of narratives and customization in a health blog on readers' attitudes, self-efficacy, subjective norms, and intention to adopt a health behavior (running for exercise). Narratives are stories with a beginning, middle, and end that provide information about the characters and plot. Customization refers to matching messages to each individual recipient. Narratives and customization have seldom been examined in tandem as strategies for effective health communication. In this dissertation, the message type (narrative vs. non-narrative) and the customization type between the blogger and each reader (no customization, health behavior-unrelated customization, and health behavior-related customization) were manipulated in a between-subjects pre-post experimental design. Findings suggest that narratives and customization can be powerful health communication tools if applied appropriately. Readers of the narrative health messages intended to engage in longer periods of running than those who read non-narrative messages. Narrative messages also outperformed non-narrative messages when the health messages were not customized, or were customized with similarities unrelated to running (e.g., both the blogger and the reader liked the color green). Bloggers who shared health-related characteristics with the reader elicited stronger intentions to run and to run for longer each time than bloggers who were similar but only on characteristics unrelated to running. The study also showed that narrative and non-narrative messages were processed differently. Customization increased effortful processing (as measured by the number of thought meaning units), but only for non-narrative messages. Narrative messages tended to elicit more positive thoughts than the non-narrative messages.