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The objective of this study was to investigate the short-term virological outcome of antiretroviral combination therapy (ART) in relation to infection with different HIV-1 genetic subtypes. Antiretroviral drug-naive patients in Sweden were prospectively enrolled and followed for 6 months when starting ART in the period from January 1998 to January 2002. Plasma-HIV-1 RNA levels, CD4 counts, and type of ART regimen were recorded. The HIV-1 subtype was determined by direct sequencing of regions of the env or pol genes. Data from 172 patients who harbored subtypes A, B, C, D, G, and CRF01_AE were analyzed (32 A, 44 B, 34 C, 18 D, 5 G, and 19 CRF01_AE). Of all patients 84% had undetectable plasma HIV-1 RNA levels after 6 months of ART. Patients infected with CRF01_AE more often had undetectable HIV-1 RNA plasma levels than patients infected with subtypes A or D. However, the possibility that this difference is due to ethnicity cannot be ruled out. Of patients of African origin, 77% had undetectable viral load after 6 months of treatment, while the corresponding figures for Caucasians and Asians were 91% and 100%, respectively. Thus, we have found an overall good short-term virological outcome after the initiation of ART in a cohort of ARV-naive patients of diverse ethnic background infected with different HIV-1 genetic subtypes. In univariate analysis ethnicity, but not genetic subtype, correlated with virological response. However, the impact of ethnicity was moderate. Patients of African origin, who had the poorest outcome, showed a 77% virological response rate.