Treatment options for HIV patients have dramatically improved since the introduction of efficacious antiretroviral combination therapy more than a decade ago. Treatment regimens have been simplified with fewer pills and fewer daily dosages. Fosamprenavir is a protease inhibitor with a rather long half-life which makes it a candidate for once-daily use. Once-daily dosage of ritonavir-boosted fosamprenavir is approved in the US, but not in Europe, for treatment in patients without prior antiretroviral treatment. Here we review the background and rationale for once-daily dosage of ritonavir-boosted fosamprenavir. The rather limited studies that have been published so far indicate that fosamprenavir 1400 mg may be used once daily boosted with ritonavir. The optimal ritonavir dose to be given together with fosamprenavir is still to be defined, though available results indicate that a dose of 100 mg may be adequate provided that no protease inhibitor resistance is present.