Baseline HIV-1 resistance testing is recommended in the 2005 BHIVA treatment guidelines. We compared the practice in our clinic with these guidelines. The aim of this study was to assess the prevalence of transmitted resistance in all antiretroviral therapy-naïve patients identified from our virology resistance test database. In 2006, 93% of all newly diagnosed patients had a baseline HIV-1 genotypic resistance test performed. The estimated prevalence of transmitted resistance was 8% in newly diagnosed patients and 7% overall with the majority in subtype B. These findings are in keeping with nationally reported data. It was of concern that we also identified a number of patients who had tested negative in the previous year.