Abstract: An improved stethoscope for use in medical diagnosis as a listening device to detect sounds within the thoracic cavity is provided having improved sound reception and transmission characteristics. The improved stethoscope has an improved stethoscope chestpiece which has two sound chambers for receiving sounds as the instrument is placed against a patient. One sound chamber is the same as that described in my earlier U. S. Pat. No. 3,067,833, utilizing a diaphragm across the mouth of the sound chamber, while the second sound chamber utilizes no diaphragm. The structure forming the second sound chamber is rotatable with respect to the structure forming the first sound chamber; rotation of the second structure with respect to the first structure between two stops results in the two chambers being acoustically connected at one position while at the second position the two chambers are acoustically insulated from each other.