HIV-1C has become the dominant HIV-1 subtype in the global AIDS epidemic. Historically, the evolution of drug-resistant mutations was characterized primarily among antiretroviral (ARV)-treated HIV-1B infections. Whereas the non-B viruses are susceptible to the currently used ARVs, some differences between HIV-1 subtypes in response to ARV regimens have been reported. We analyzed the profile of ARV-associated mutations in HIV-1C infection treated with ZDV/ddI-containing regimens in an open-label, randomized 3 x 2 x 2 factorial study comparing ZDV/3TC vs. ZDV/ddI vs. d4T/3TC and EFV vs. NVP regimens in drug-naive adults in Botswana. The overall rate of virologic failure in the ZDV/ddI-containing arms was 14%. We addressed the development of NRTI-associated mutations in 23 virologically failed patients in the ZDV/ddI-containing arms. The 67N 70R 215Y genotype with wild-type amino acids at codon positions 41 and 210 was a dominant pattern of NRTI-associated mutations at the time of virologic failure. The mutation T215Y was the first step in the evolution of the 67N 70R 215Y genotype and was followed by mutations K70R and D67N. Representing a mixture of TAM-1 (41L/210W/215Y) and TAM-2 (67N/70R/215F /219Q) pathways, the 67N 70R 215Y genotype with wild-type amino acids at codon positions 41, 210, and 219 is a unique TAM pathway that is rarely seen in HIV-1B infection. Although limited by relatively small numbers, our data suggest that the 67N 70R 215Y genotype may be the HIV-1C-specific response to the first-line ZDV/ddI-containing regimen at the time of virologic failure. The presence of the 67N 70R 215Y genotype with wild-type amino acids at codon positions 41, 210, and 219 in HIV-1C infection suggests that the evolution of ARV-associated mutations and TAM pathways might be unique in non-B HIV-1 subtypes treated with particular ARV regimens.