Elevated aspartate aminotransferase-to-platelet ratio index (APRI) may signal liver fibrosis. Among 397 US children with perinatal HIV infection, APRI at baseline was > 1.5 in 0.8% (95% confidence interval [CI], 0.2–2.2%) and > 0.5 in 6.5% (95%CI, 4.3–9.4%); incidence on study was 0.5 (95%CI, 0.2–1.2) and 6.4 (95%CI, 4.8–8.3) per 100 person-years, respectively. Long-term liver outcomes after perinatal HIV infection warrant further study.