In September of 1993 API published a new section of the Manual of Petroleum Measurement Standards titled Chapter 21 Flow Measurement Using Electronic Metering Systems, Section 1 Electronic Gas Measurement. This report provides an overview of the API 21.1 document with the intent of serving as a primer and something of an introduction to the publication. The 21.1 standard was developed by representatives from the American Petroleum Institute (API), American Gas Association (AGA) and Gas Processors Association (GPA) member companies with input from equipment manufacturers and others. The 21.1 standard represents the first API publication in the field of electronic metering systems