To examine the effects of Hurricane Katrina on the disease progression of persons living with HIV/AIDS (PLWH/A), CD4 counts during the 18 months immediately prior and subsequent to Katrina were obtained from the Louisiana Office of Public Health. PLWH/A were determined to be either non-residents of the New Orleans area, returning evacuees or evacuees who had returned to the area within 18 months. A mixed model repeated measures ANOVA showed significant effects for race, sex, age, year of diagnosis, and mode of exposure. A significant main effect for residence was found, as well as an interaction of residence by time of CD4 count (pre-Katrina vs. post-Katrina), indicating that, while non-returning evacuees had lower overall CD4 counts, the change in CD4 counts of non-returning evacuees dropped more sharply than those of the returning PLWH/A or non-residents. While these results point to a potential need for the population of PLWH/A who continue to be affected by Katrina, they also provide important data on the effect that large-scale disasters and stressful life events may have on individuals with chronic disease.