Objective To investigate the relations between Medical Research Council (MRC) dyspnea grade and peripheral muscle force, activities of daily living (ADL) performance, health status, lung function, and exercise capacity in subjects with idiopathic pulmonary fibrosis (IPF). Design Prospective cross-sectional observational study. Setting University hospital. Participants Subjects with IPF (N=65, 46 men) in a stable clinical state with a mean age of 68±7 years. Interventions Not applicable. Main Outcome Measures Right ventricular systolic pressure (RVSP) via transthoracic echocardiography, pulmonary function, isometric quadriceps force (QF) and handgrip force (HF), 6-minute walk distance (6MWD), ADL score, and health status (Medical Outcomes Study 36-Item Short-Form Health Survey [SF-36]) were assessed and compared between subjects grouped according to MRC grade. Results Of the participants, 16 were in MRC grade 2, 17 were in MRC grade 3, 17 were in MRC grade 4, and 15 were in MRC grade 5. RVSP, pulmonary function, QF, HF, 6MWD, ADL, and SF-36 scores decreased with increasing MRC grade (all P.56, P=.001). Conclusions The MRC dyspnea scale provides a simple and useful method of categorizing individuals with IPF with respect to their activity limitation and may assist in understanding the impact of IPF on an individual. © 2014 by the American Congress of Rehabilitation Medicine.