Optimists (people who have positive expectations about the future) have been shown to perform more health-promoting behaviors than pessimists. This study attempts to alter individuals' levels of optimism, and thereby their health behaviors, by having them write about a positive future. HIV-infected women (N = 40) on combination therapies were randomly assigned to write about a positive future or assigned to a no-writing control group. Among participants who were low in optimism, the writing intervention led to increased optimism, a trend toward increased self-reported adherence to medications, and decreased distress from medication side effects, compared to controls who did not write. Participants who were high in optimism showed the opposite effects after writing about the future. Results suggest that a future-oriented writing intervention may be a promising technique to increase medication adherence and decrease symptom distress in pessimistic individuals.