This paper discusses fundamental issues relative to ultrasonic gas flow meters used for measurement of natural gas. A basic review of an ultrasonic meter’s operation is presented to understand the typical operation of today’s Ultrasonic Gas Flow Meter (USM). The USM’s diagnostic data, in conjunction with gas composition, pressure and temperature, will be reviewed to show how this technology provides diagnostic benefits beyond that of other primary measurement devices. The basic requirements for obtaining good meter performance, when installed in the field, will be discussed with test results. Finally, recommendations for installation will be provided, including an example of a good piping design