Rationale: IPF is an interstitial lung disease with high mortality. Two antifibrotic medications, nintedanib and pirfenidone, were approved for the treatment of IPF in the US in October 2014. Little is known about use of these medications in practice. Methods: The IPF-PRO Registry enrolls patients with IPF that is newly diagnosed or newly confirmed at the enrolling centers. Enrollees are followed prospectively while receiving usual care, including review of antifibrotic medication use at enrollment and approximately 6 months later. Data from patients enrolled from 5 June 2014 to 1 May 2018 were used to determine antifibrotic medication use patterns at enrollment. Patients with documented medication use prior to or ≤3 months after enrollment were “treated” at enrollment; others were “untreated”. Among patients with documented medication review between 3 and 8 months after enrollment, patients with documented medication use in this window were “treated” during follow-up and others were “untreated”. Follow-up treatment status was unavailable in some cases. Analyses were descriptive. Results: At enrollment, 554 (67.1%) of 826 eligible patients were treated and 272 (32.9%) were untreated (Figure). Among 405 patients treated at enrollment and with available data on medication use at follow-up, 379 (93.6%) remained treated during follow-up and 26 (6.4%) stopped treatment. Data on medication use at follow-up was unavailable in 149 (26.9%) patients treated at enrollment. Among 114 patients untreated at enrollment and with available data on medication use at follow-up, 34 (29.8%) started treatment during follow-up and 80 (70.2%) remained untreated. Data on medication use at follow-up was unavailable in 158 (58.1%) of those untreated at enrollment. At enrollment, in the treated versus untreated groups, respectively, median FVC was 68.7% versus 71.5% predicted, DLco was 41.7% versus 43.8% predicted, and SGRQ total score was 40.6 versus 35.4; the proportions of patients with a definite diagnosis of IPF were 69.7% versus 65.0% and the proportions of patients receiving supplemental oxygen at rest were 21.6% versus 14.6%. Conclusions: Approximately two-thirds of IPF-PRO Registry enrollees were receiving an FDA-approved medication to treat IPF at enrollment. Among enrollees with medication use review during follow-up, most patients treated at enrollment remained treated, and over one-quarter of patients untreated at enrollment initiated medication during follow-up. By some measures, treated patients had more severe disease than untreated patients at time of enrollment. These data provide insight into the use of medications to treat IPF in clinical practice, which will grow with further registry follow-up.