HIV-1 resistance testing has become an increasingly important feature in antiretroviral treatment and is commonly accomplished by genotyping. Currently, two different systems are being marketed and, despite being far from easy to use, have achieved a high degree of sophistication. Modifications of the standard-kit protocols may be advantageous in certain situations. Although resistance reports are issued by these systems through interpretation software based on decision rules, it nevertheless requires considerable knowledge and skills by the user to make useful clinical data out of detected resistance patterns. This review describes both systems in detail and discusses their advantages and disadvantages. A final decision on which system to use must be based on an individual's requirements. The future of this field may lie with the use of microarray systems.