Suspected hypersensitivity is the main reason for the early discontinuation of abacavir. After the observation that the risk of hypersensitivity correlated with ethnicity, the presence of the HLA allele B5701 was found to be the strongest retrospective predictor of hypersensitivity. Two prospective cohorts have since demonstrated a significant reduction in abacavir hypersensitivity rates with the use of prospective human leukocyte antigen screening. We describe our experience of prospective HLA-B5701 testing and the impact on rates of abacavir hypersensitivity.