We have designed a novel, precise, and sensitive assay to measure unspliced (US) human immunodeficiency virus type 1 (HIV-1) mRNA in peripheral blood mononuclear cells of HIV-1-infected individuals by using real-time PCR and molecular beacons. Individuals were classified as either well suppressed (WS) or partially suppressed, based on longitudinal measurements of plasma HIV-1 RNA. The proportion of individuals with US mRNA undetectable over time was significantly higher among WS individuals; however, 30% of WS subjects still had detectable US mRNA after 24 months of effective antiviral therapy.