The objective of this post-marketing surveillance study is to evaluate the incidence of adverse events in Japanese subjects with pulmonary arterial hypertension treated with ambrisentan basd on prescribing information under the conditions of general clinical practice and also to grasp the following items;

1. Unknown adverse drug reactions (ADRs)
2. Incidence of ADRs to medical products in actual clinical practice
3. Factors influencing safety of ambrisentan
4. Factors influencing efficacy of ambrisentan
5. Prognosis of subjects as well as efficacy and safety of ambrisentan in long-term use (VOLIBRIS® is a trademark of Gilead Sciences, Inc,. that GSK uses under license.)

Inclusion Criteria:

• Must use ambrisentan for the first time

Exclusion Criteria:

• Subjects with hypersensitivity to ambrisentan
• Subjects who is pregnant or might be pregnant
• Subjects with severe hepatic disorder

All Japanese subjects who have received ambrisentan for the first time for the treatment of pulmonary arterial hypertension (PAH) and have given their consent to participate in the study.