It is generally accepted that HIV-infected pregnant women should receive treatment to prevent the transmission of HIV from mother-to-child.The (relative) contra-indications for the NNRTIs during pregnancy make a PI based regimen the most rational choice. Based on several experiences and investigations it is expected that saquinavir will play a role as a component of tripe drug regimens for HIV-infected pregnant women. Since the bid dose regimen of 1,000mg saquinavir and 100mg ritonavir is approved by the regulatory authorities and with the availability of a new 500mg tablet formulation of saquinavir,there is a need for a well-designed pharmacokinetic trial using the new 500mg saquinavir tablet formulation in the above mentioned dose.