<p>Pill counts with calculated adherence percentages are used in many settings to monitor adherence, but can be undermined by patients discarding pills to hide non-adherence. Pill counts suggesting that &gt;100% of prescribed doses were taken can signal "pill dumping." We defined "over-adherence" (OA) among a cohort of 300 HIV-infected adolescents as having &gt;1/3 of pill counts with &gt;100% adherence during a year of follow-up. Apparent over-adherence was more common in those with virologic failure than those with suppressed viral loads (33% vs 13%, chi p=0.001). Pill count adherence repeatedly &gt;100% may identify HIV-infected adolescents at increased risk of treatment failure.</p>