Current guidelines for referring patients with idiopathic pulmonary fibrosis (IPF) for lung transplantation, based on resting parameters, are insufficient to predict 3-year mortality. The aim of this study was to determine the prognostic value of cardio-pulmonary exercise testing (CPET) in patients with IPF. A multicentre retrospective study of 3-year outcome was made on 63 adult patients with IPF who underwent CPET with blood gas analysis. Demographic data, resting pulmonary function and CPET parameters were collected to perform a univariate survival analysis. To estimate prognosis at 3 years, a multivariate logistic regression analysis by Kaplan-Meier curves and log-rank tests was performed. Forty-four patients (70%) were alive without lung transplant at the end of the 3-year follow-up: 19 patients (30%) were dead (n=14) or transplanted (n=5). Univariate analysis indicated that: at rest lower TLC, FVC, DLCO and PaCO(2), higher alveolo-arterial gradient for oxygen [P(A-a)O(2)] and pH; at ventilatory threshold (VT) higher VE/VO(2) and VE/VCO(2) and at peak exercise higher VE/VO(2) and VE/VCO(2), higher pH and ΔP(A-a)O(2)/ΔVO(2) (mmHg/L), lower VO(2) peak, PaO(2) and VO(2)/FC were associated with a significantly lower survival at 3 years. The multivariate logistic regression analysis showed that CPT (<65%) and VE/VO(2) at VT (>45) were independently associated with a lower survival at 3 years. Restriction and hyperventilation at ventilatory threshold are major prognostic factors in the course of IPF. CPET with blood gas analysis may have a prognostic value in these patients and initial evaluation of these parameters can help to predict disease progression.