Some researchers have proposed strategies whereby patients alternate or cycle back and forth between two or more different antiretroviral drug regimens. This is based on the theory that regularly switching drugs might reduce the length of time a person is exposed to a failing regimen, thereby minimising the emergence of drug resistance. The SWATCH study, for example, found that patients who alternated between AZT/3TC/nelfinavir and d4T/ddI/efavirenz experienced treatment failure later than those who stayed on a single regimen ^[1]. However, other research has not been as promising, and this strategy has largely fallen out of favour.