Hurricane Katrina disrupted HIV/AIDS surveillance by invalidating the New Orleans, La, surveillance and population data on persons living with HIV/AIDS. We describe 2 methods--population return and HIV surveillance data--to estimate the return of the infected population to New Orleans. It is estimated that 58% to 64% of 7068 persons living with HIV/AIDS returned by summer 2006. Although developed for HIV planning, these methods could be used with other disease surveillance programs.