Background: A growing body of evidence suggests that high rates of incarcerated people and high levels of HIV coexist and that people with HIV/AIDS in prisons have histories of cumulative trauma and stress. Almost inevitably, a prison population is an aging population. The purpose of this study was to provide a general method for valuing the benefits of not having HIV using the preferences of prisoners so that these can be compared to the costs in order that a Cost-Benefit analysis of HIV interventions can take place. Methods: The proposed method involves representing the utility function of an incarcerated person as being determined negatively by the presence of having HIV, and positively by having an income, and then finding the marginal rate of substitution between having HIV and giving up some income. A regression equation is used to estimate the utility function where the Centers for Disease Control and Prevention’s (CDC’s) health-related quality of life is used to measure utility. Apart from HIV and income the regression equation has life stressors and age as controls. We use a sample of 516 incarcerated adults from a self-reported survey, consisting mainly of persons aged 50 and older housed in a Northeastern prison system, to apply our methods. Results: Our regression analysis showed that four life stressors and age were significant and important as controls for HIV/AIDS status and income in determining an incarcerated person’s quality of life. Our best estimate of the benefit of not having HIV in a prison setting was around $350,000. Conclusion: The value of not having HIV in a prison setting is large. This value could make many existing interventions to prevent HIV/AIDS be shown to be to be socially worthwhile as they would pass a Cost-Benefit test. Our finding of the importance of life stressors for a prison population with HIV would suggest that interventions that involve the prevention of traumatic experiences in early childhood could also be socially worthwhile as they would both help to prevent HIV/AIDS and lessen the impact on quality of life if HIV were to occur. Targeting older prisoners with HIV should also be a priority as their quality of life is significantly lower than for younger prisoners.