['In a large number of patients on HAART who achieved plasma HIV RNA levels below the limit of detection (50 copies/ml), transient relapses of HIV RNA levels ("blips") are observed.', 'To determine whether relapses of plasma HIV RNA during HAART are associated with development of drug resistance.', 'Plasma samples from 15 patients with a transient viral load relapse during HAART were studied. All regimens contained lamivudine (3TC). We used an ultrasensitive sequence approach to analyze the presence of drug resistance mutations during the relapse.', 'The median plasma HIV RNA load of the relapse was 76 copies/ml (range 50-1239). In 11 of 15 cases, a genotype of HIV could be obtained. Mutations in the RT and protease gene conferring resistance to one or more drugs were observed in 8 of 11 patients, 6 of whom had the M184V substitution. During a median follow-up of 27 months after the relapse, plasma HIV RNA levels remained undetectable in 13 of 15 patients.'] Are transient relapses ( `` blips '' ) of plasma HIV RNA levels during HAART associated with drug resistance?