The aims of this retrospective study are to assess the prevalence of primary resistances to antiretroviral drugs, both reverse transcriptase and protease inhibitors in untreated patients from Spain, and to determine their possible association with several epidemiological variables. A total of 148 samples belonging to 145 patients were processed using the genotypic technique VERSANT HIV 1 (LiPA) in order to study the presence of mutations at codons 41, 69, 70, 74, 75, 103, 106, 151, 181, 184 and 215 of the reverse transcriptase gene (VERSANT HIV 1 RT) and at codons 30, 46, 48, 50, 54, 82, 84 and 90 of the protease gene (VERSANT HIV 1 Protease). The patients' epidemiological variables which could be relevant to HIV infection were also analyzed. The successful amplification rate was 77.70% for LiPA RT and 91.21% for LiPA P. In the case of LiPA RT, statistical significance (p < 0.05) was observed when successful amplification was related to viral load level (p < 0.001). Global prevalence of resistance was 20.27%. Mutations in the reverse transcriptase gene were found in eight samples (5.40%). Using LiPA P, mutations were detected in 16.21% of cases, with V82A being the most frequently detected mutation (15/24, 62.50%) in nine samples. The V82A mutation was found alone (66.6%) and it was found together with the I84V mutation in five samples (20.83%). I84V was the second most frequently detected mutation (13/24, 54.16%). No statistical significance was found for any of the epidemiological variables. Due to the problems encountered in a high percentage of samples, the authors concluded that the amplification technique should be improved. The prevalence of resistance detected was around the mean of that found by other authors.