We present a clinical case of antiretroviral treatment failure with appearance of mutations demonstrated by genotyping. We also show the evolution of the pattern of mutations that confers resistance to protease and reverse transcriptase inhibitors along with changes in the scheme of drugs indicated to the patient. A deletion was found in codon 67 of the TR gen, along with a novel resistance model to AZT pointing out the benefits of the detection of antiviral resistance by sequencing (genotyping).