The purpose of this study is to provide sildenafil therapy to patients who completed the A1481244 study for the treatment of PAH, and reside in Brazilian States where Revatio™ is not supplied by Health Secretary, and are judged by the Investigator to derive clinical benefit from continued treatment with Sildenafil. It will be supplied until patient gets access to Sildenafil through Brazilian State Health Secretary from where patient resides.

Inclusion Criteria:

• Subject who completed the A1481244 study and are judged by the Investigator to derive clinical benefit from continuous treatment with Sildenafil 20 mg therapy.
• Subject who resides in a Brazilian State where Sildenafil is not supplied by State Health Secretary.

Exclusion Criteria:

• Pregnant or lactating women.
• Current participation in other studies and during study participation.