The drug resistance profile of treatment-naive HIV-infected individuals living in Buenos Aires, Argentina, was studied. Samples taken from 94 drug-naive individuals with established HIV infection and 13 patients with primary HIV infection were assessed by nucleotide sequencing and LIPA. The prevalence of drug-associated primary mutations in individuals with established infection was very low. In the viral protease region, 1/86 (1.2%) individuals carried the D30N mutation, whereas 1/85 (1.2%) had the M41L mutation in the reverse transcriptase (RT) region. Secondary mutations in both the protease and RT regions were found in almost 90% of the individuals. In individuals with primary infection, primary mutations were detected in 2/13 (15.4%) patients, one of them carrying M461 mutation in the protease while the other patient had a mutation at codon 184 of the RT. In accordance with current drug resistance testing guidelines, the results of this study suggest that susceptibility tests need not be performed at this time prior to initiation of antiretroviral therapy in HIV-1-infected people in Argentina. However, the public health implications of this subject warrant follow-up studies that will examine a larger number of drug-naive patients, not only in Buenos Aires but also in other major Argentinian cities and in rural areas.