Managed care organizations (MCOs) may be incurring financial losses from persons with human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) (PWHA). This study developed a statistical model to examine which specific comorbidities are important contributors to the variations in health care costs of PWHA. Individuals were classified into cost groups to simulate biased selection in MCOs. Capitation payments for various cost groups under different methodologies were compared. The statistical model closely matched payments with the actual costs of care. Capitation payments for HIV/AIDS enrollees based on this model will better protect MCOs than the traditional risk-adjustment methods.