To evaluate measurements of respiratory sensation in ILD, we compared ratings of breathlessness from three clinical scales with the perceived magnitude of added elastic loads in 20 symptomatic ILD patients. Dyspnea ratings were obtained by two independent observers for each clinical method. Perceived magnitude of four elastic loads was selected from the Borg category scale; these estimates were summarized using the psychophysical power function equation. Ten age-matched healthy subjects also scaled the magnitude of added elastic loads. Dyspnea ratings from the three clinical scales were significantly interrelated. Mean exponents for mouth pressure developed during elastic loading were similar in the patient and control groups. Dyspnea ratings and exponents for elastic loads were not significantly correlated in ILD patients. Of the physiologic parameters examined, Dsb and gas exchange during exercise correlated significantly with clinical dyspnea ratings; none correlated with the exponent for added elastic loads. These data demonstrate that clinical dyspnea ratings provide valid measures of breathlessness in patients with ILD which are independent of the perception of respiratory loads.