| Subjects n | 748 |
| Age years | 66±7.6 |
| Sex | |
| Male | 535 (71.5) |
| Female | 213 (28.5) |
| Ethnicity | |
| Caucasian | 703 (94.0) |
| Other | 45 (6.0) |
| Country of residence | |
| USA | 521 (69.7) |
| Other | 227 (30.3) |
| Treatment assignment | |
| Interferon γ-1b | 496 (66.3) |
| Placebo | 252 (33.7) |
| Clinical | |
| Honeycombing on HRCT | 653 (87.3) |
| Surgical lung biopsy | 411 (54.9) |
| History of cardiovascular disease | 213 (28.5) |
| Supplemental oxygen use | 115 (15.4) |
| Physiological characteristics | |
| FVC % predicted | 72.5±12.8 |
| DLCO % predicted | 47.5±9.2 |
| 6MWT distance m | 397±107 |
Data are presented as mean±sd or n (%). HRCT: high-resolution computed tomography; FVC: forced vital capacity; DLCO: diffusing capacity of the lung for carbon monoxide; 6MWT: 6-min walk test.