BACKGROUND: Pulmonary hypertension (PH) is commonly seen in patients with idiopathic pulmonary fibrosis (IPF). We sought to examine the relationship between pulmonary function tests (PFTs), including the percentage of predicted FVC (FVC%), percentage of predicted total lung capacity, percentage of predicted diffusing capacity of the lung for carbon monoxide (Dlco%), the composite physiologic index (CPI), and PH. The ability of FVC%, Dlco%, and FVC%/Dlco% ratio to predict underlying PH was assessed. METHODS: Retrospective review of IPF patients seen at a tertiary referral center over an 8-year interval in whom both PFT and right-heart catheterization data were available. RESULTS: The study cohort consisted of 118 patients, of whom 48 patients (40.7%) had PH. There was no correlation between measures of lung volumes or the CPI with underlying PH. There was a modest association between Dlco% and PH, with Dlco% < 30 having a twofold-higher prevalence of PH (56.4%) compared to Dlco% >/= 30 (28.6%). Cardiac dysfunction might have played a small role, since 16.1% of the patients had an associated elevated pulmonary capillary wedge pressure. There was a trend to a higher prevalence and greater severity of PH in those patients with FVC% > 70 compared to the group with FVC% < 40. CONCLUSION: PH is common in patients with IPF. There is a poor correlation between lung function measures and PH, suggesting that factors other than fibrosis may play a role in the etiology. The unexpected high prevalence and severity of PH in patients with well-maintained lung function have implications for the prognosis and management of the disease.