BACKGROUND: The aim of the study was to quantify the risk of a drop in CD4 counts below 200 cells/μL after reaching values >350 cells/μL on antiretroviral therapy (ART) (or after starting ART with CD4 count >350 cells/μL) in the absence of virological failure. SETTING: Ambulatory care services, Italy. METHODS: Prospective cohort study of patients enrolled in the ICONA Foundation Study cohort who started ART with >350 CD4/μL or with ≤350 CD4/μL and reached values >350 cells/μL after virological suppression (VS, defined by 2 consecutive viral loads ≤50 copies/mL). The date of CD4 count >350 was the baseline for the analysis and those with ≥1 viral load and CD4 count after baseline were included. The primary end point was the cumulative risk (estimated using the Kaplan-Meier method) of a CD4 drop below 200 cells/μL over follow-up, which was censored at the date of virological failure (confirmed HIV-RNA >50 copies/mL), death, or last visit. RESULTS: Six thousand six hundred sixty-three patients were included. A confirmed CD4 drop below 200 cells/μL was never observed over a median follow-up of 45 (Q1: 21, Q3: 89) months, as long as VS was maintained. Upper limits of the 97.5% confidence interval of rates of confirmed CD4 drop below 200 cells/μL were 0.28 and 0.38/1000 person-years of follow-up for patients with ≤350 and >350 CD4 cells/μL at starting ART. CONCLUSIONS: In patients who started ART in Italy with >350 CD4 cells/μL or reached >350 CD4 cells/μL after VS, the risk of a CD4 drop below 200 cells/μL in those maintaining VS was negligible.