Interobserver variation was studied for 11 respiratory signs and for the diagnostic conclusions made on the basis of these signs. Two physicians each, with and without knowledge of the patient's history, performed physical examination of the lungs in a total of 202 unselected patients from a department of internal medicine. The interobserver variation was calculated as the kappa coefficient, using a modified method that made it possible to calculate the interobserver variation for a pair of observers made up by varying physicians. No difference was demonstrated between the kappa coefficients obtained for examinations performed with and without knowledge of the history. The kappa values for the signs ranged from -0.04 to 0.58, and for the diagnoses from 0.15 to 0.68, i.e., expressed by kappa values, poor agreement. In a questionnaire study we asked a number of physicians from departments of internal medicine to guess the size of the interobserver variation for the 11 respiratory signs examined. A total of 47 physicians (90%) returned the questionnaire and the answers showed that the physicians markedly underestimated the interobserver variation.