Male or females from 40 to 80 years of age

Diagnosis of IPF

Honeycombing (fibrosis in the lung) on high-resolution computerised tomography (HRCT) scan of less than or equal to 5%

Willing and able to have 2 right heart catheterizations performed

Willing to have monthly lab tests to monitor liver function

Able to perform the 6 minute walk test (indicated adequate physical function)

Must have meet lung function requirements

Normal liver function tests

Negative serum pregnancy test

Willing to use at least 2 reliable methods of contraception

Able to understand and willing to sign informed consent form

(ARTEMIS-IPF) Randomized, Placebo-Controlled Study to Evaluate Safety and Effectiveness of Ambrisentan in IPF