The prognosis of patients with idiopathic pulmonary fibrosis (IPF) is generally considered to be poor. As the disease progresses, patients invariably become severely limited in their activities. Therefore, evaluating the health-related quality of life (HRQoL) in IPF patients is considered to be important. However, there have been few studies of this kind to date. We applied the St. George's Respiratory Questionnaire (SGRQ) to 41 consecutive IPF patients and examined various physiological variables to identify factors that were correlated with the HRQoL. Total lung capacity, transfer factor, arterial partial pressure of oxygen at rest, the lowest oxygen saturation during exercise test, and the baseline dyspnoea index (BDI) score were significantly correlated with the total SGRQ score. A similar tendency was observed in each component. Conversely, peak oxygen uptake, known as one of the important factors that determines HRQoL in chronic obstructive pulmonary disease (COPD), did not correlate with any SGRQ scores. In stepwise multiple regression analysis, the BDI score was selected as the only factor significantly contributing to the total SGRQ score. Dyspnoea was the most important factor determining HRQoL in IPF. The types of other variables that correlated with the HRQoL in IPF patients were different from those in COPD.