A growing body of evidence suggests that antiretroviral resistance is associated with an increased risk of disease progression and death. All commercially available antiretrovirals and many of those in development have been associated with resistance. Fortunately, techniques are available to define HIV genotypic resistance in "real time" as compared to techniques that measure phenotypic resistance that is not practical in a clinical setting. Using genotypic antiretroviral resistance testing (GART) results, along with other currently available markers, may lead to improved treatment decisions compared with using currently available markers alone.