This study explored the effects of expressive writing on positive and negative outcomes related to perceived psychosocial and health status among persons with HIV. This was the first study to examine the moderating effects of cognitive adaptability--consisting of dispositional optimism coupled with perceived competence--on outcomes of expressive writing. Thirty-seven participants wrote about either traumatic experiences or trivial topics in four 20-min sessions. Dependent measures obtained at baseline were repeated 1 month later. Although no main effects for group were found, baseline levels of cognitive adaptability were differentially associated with changes in a positive outcomes index, and a pain and physical functioning index in those assigned to the two groups. No moderating effects of cognitive adaptability were found for changes in a negative outcomes index. Findings underscore the importance of identification of moderating variables in understanding the impact of expressive writing interventions among individuals with HIV or other conditions.