We recently reported that interleukin-7 (IL-7), a potent stimulator of lymphopoiesis, is an independent predictor of virological response to antiretroviral therapy (ART) in HIV-1 infected adults. To determine if this cytokine also predicts treatment response in HIV-1-infected children, a longitudinal study was performed over 48 weeks in 36 treatment-naïve children vertically infected with HIV-1. Subjects who received treatment (n = 29) were stratified as complete virological responders (n = 12), partial virological responders (n = 11), or non-responders (n = 6), based on decline in viral load from baseline to week 48. Median plasma IL-7 levels at baseline were higher in complete responders (4.85 pg/mL, interquartile range [IQR] = 3.35-6.5) than in untreated controls (2.10 pg/mL, IQR = 1.50-3.50; p = 0.05). Linear regression analysis showed that baseline IL-7 levels were positively correlated with changes in HIV-1 viral load between baseline and week 24 (r = 0.40; p = 0.03) and between baseline and week 48 (r = 0.34; p = 0.07), but not with corresponding changes in CD4+ T-cell percentages and absolute counts. Collectively, these results indicate that IL-7 levels at baseline are predictive of virological but not immunological response to ART in children infected with HIV-1.