Importance: Despite the introduction of combination antiretroviral therapy (cART), HIV-associated neurocognitive disorders continue to be a problem for treated HIV-positive individuals. The cause of this impairment remains unclear. Objective: To determine if detectable brain changes occur during a 2-year period in HIV-positive individuals who were aviremic and treated with cART. Design, Setting, and Participants: In this longitudinal case-control study, participants underwent neuroimaging and neuropsychological assessment approximately 2 years apart. Data were collected from October 26, 2011, to March 1, 2016. Data from 92 HIV-positive individuals were acquired atWashington University in St Louis from ongoing studies conducted in the infectious disease clinic and AIDS Clinical Trial Unit. A total of 55 HIV-negative control participants were recruited from the St Louis community and a research participant registry. A total of 48 HIV-positive individuals who were aviremic and treated with cART and 31 demographically similar HIV-negative controls met the study requirements and were included in the analyses. Main Outcomes and Measures: Brain volumeswere extracted with tensor-based and voxel-based morphometry and cortical modeling. Raw scores from neuropsychological tests quantified cognitive performance. Multivariable mixed-effects models assessed the effect of HIV serostatus on brain volumes and cognitive performance, and determined if HIV serostatus affected how these measures changed over time. With HIV-positive participants, linear regression models tested whether brain volumes and cognitive performance were associated with measures of infection severity and duration of infection. Results: The 2 groups were demographically similar (HIV-positive group: 23 women and 25 men; mean [SD] age, 47.7 [13.2] years; mean [SD] educational level, 13.3 [3.4] years; and HIV-negative group, 16 women and 15 men; mean [SD] age, 51.2 [12.9] years; mean [SD] educational level, 14.5 [2.1] years). The HIV-positive participants had poorer neuropsychological test scores compared with controls on the Trail Making Test Part A (5.9 seconds; 95%CI, 1.5-10.3; P = .01), Trail Making Test Part B (27.3 seconds; 95%CI, 15.0-39.6; P < .001), Digit Symbol Substitution Task (-12.5 marks; 95%CI, -18.9 to -6.0; P < .001), Letter-Number Sequencing (-2.5 marks; 95%CI, -3.7 to -1.3; P < .001), Letter Fluency (-6.6 words; 95%CI, -11.5 to -1.6; P = .01), and Hopkins Verbal Learning Test-Revised immediate recall (-2.4 words; 95%CI, -4.4 to -0.4; P = .05), after adjusting for age, sex, and educational level. Only changes in Trail Making Test Part A significantly differed between the groups. Cortical thickness and subcortical volumes were smaller in HIV-positive individuals compared with controls. However, changes in brain volume over time were similar between the groups. Conclusions and Relevance: These findings are consistent with the idea that cognitive and structural brain changesmay occur early after seroconversion, and argue that maintaining aviremia with cART can prevent or minimize progressive brain injury. © 2017 American Medical Association. All rights reserved.