Two critically important issues in human immunodeficiency virus (HIV) therapeutics are when to start antiretroviral therapy and how well these medications restore immunity. In this issue of JAMA Internal Medicine, Okulicz et al1 describe a prospective cohort study of 1119 US military service persons with known seroconversion dates who were monitored for several years. Because the dates of seroconversion were known for these individuals and their immunologic status was well characterized, the data from this valuable cohort enable us to better answer these fundamental questions about HIV treatment.