3. Only if RVSP is unable to be estimated on an echo at NIH, the absence of the following abnormalities on echo will be used: right ventricular enlargement, right ventricular hypertrophy, paradoxical movement of interventricular septum and/or altered pulmonary flow velocity. If RVSP is unable to be estimated and these abnormalities are absent on echo, the patient will be enrolled as an ILD-only patient. If any of these echocardiographic abnormalities are present the patient will not be enrolled until the results of a right heart catheterization can be obtained to verify the absence of pulmonary hypertension.