ASTM G 175 is a standard test method for evaluating the ignition sensitivity and fault tolerance of oxygen regulators used for medical and emergency applications. To show the ASTM G 175 test method was repeatable at different laboratories, a series of interlaboratory tests were performed on medical oxygen regulators in late 2002. These tests were performed on six regulator designs at three laboratories. Three of the regulator models employed a compressed gas association (CGA) 870-style connection and the other three regulator models used a CGA 540-style connection. Five of the regulators were commercially available and the other one was a CGA 870-style regulator that was intentionally designed to fail the test. The results of the round robin tests are presented and discussed.