There is significant heterogeneity in survival time among patients with idiopathic pulmonary fibrosis. Studies of baseline clinical and physiologic variables as predictors of survival time have reported inconsistent results. We evaluated the predictive value of changes in clinical and physiologic variables over time for survival time in 81 patients with biopsy-proven idiopathic pulmonary fibrosis. Six-month changes in dyspnea score, total lung capacity, thoracic gas volume, FVC, FEV₁, diffusing capacity of carbon monoxide, partial pressure of arterial oxygen, oxygen saturation, and alveolar–arterial oxygen gradient were predictive of survival time even after adjustment for baseline values. Analyses were repeated on 51 patients with 12-month change data. Twelve-month changes in dyspnea score, total lung capacity, FVC, partial pressure of arterial oxygen, oxygen saturation, and alveolar–arterial oxygen gradient were predictive of survival time after adjustment for baseline values. Evaluation of changes in clinical and physiological variables over 6 and 12 months may provide clinicians with more accurate prognostic information than baseline values alone.