OBJECTIVES: To investigate, using a longitudinal design, whether biomarkers of cardiovascular risk change after a switch to an abacavir (ABC)-containing regimen in HIV-1-infected individuals already receiving combination antiretroviral therapy (ART). METHODS: Thirty-five HIV-1-infected individuals who switched ART to an ABC-containing regimen were identified. Twenty-two HIV-1-infected individuals who switched ART from and to a non-ABC-containing regimen served as controls. Plasma concentrations of soluble vascular cell adhesion molecule 1 (sVCAM-1), soluble intercellular adhesion molecule 1 (sICAM-1), matrix metallopeptidase 9 (MMP9), myeloperoxidase (MPO) and high sensitivity C-reactive protein (hs-CRP) were measured in blood samples before the switch in ART, and 3 months and 12 months afterwards. Log10-transformed data were compared with paired t-tests. RESULTS: Median MMP9 increased from 45.5 to 64.4 microg/mL after 3 months of ABC exposure (P = 0.011) and remained increased after 12 months (64.2 microg/mL; P = 0.013). MPO increased from median 8.8 to 10.4 microg/mL (P = 0.036) after 3 months of ABC exposure but was not increased after 12 months of exposure (9.1 microg/mL). hs-CRP increased from 3.3 to 4.2 microg/mL after 3 months (P = 0.031) but was not increased after 12 months of exposure (2.8 microg/mL). Neither sVCAM-1 nor sICAM-1 changed after the initiation of ABC. No changes were observed in the control group. CONCLUSIONS: MMP9, MPO and hs-CRP all increased after a switch in ART to an ABC-containing regimen. This indicates increased cardiovascular risk in viral load-suppressed HIV-1-infected individuals switching to ABC and proposes a proinflammatory potential as the underlying pathogenetic mechanism.