The performance of the new version of RT-PCR assay (Amplicor(TM) HIV-1 Monitor(TM) v1.5) was assessed. The quantification of non-B subtype HIV-1 plasma RNA (30A, 1C, 1D, 3E, 2F, 3G) obtained using Monitor(TM) v1.5 was compared to the former version of this assay (Monitor(TM) v1.0) and to the Quantiplex(TM) v2.0 bDNA assay. The new primers used in Monitor(TM) v1.5 were similar to the former version in both specificity and sensitivity. The new primers corrected the detection and quantification defect observed previously for HIV-1 non-B subtypes and gave slightly higher RNA concentrations than those measured using the bDNA assay (+ 0.39 log copies/ml). (C) Published by 1999 Elsevier Science B.V. All rights reserved.