This tutorial will give information about the IEEE Guide for application and use of gas-insulated transmission lines for voltage of 72.5 kV and above. The content of the tutorial covers the following topics: guidance for the planning, permitting, design, equipment specification, installation, commissioning, operation, and maintenance of gas-insulated transmission lines. Only technical aspects will be addressed in this guide; commercial and legal issues associated with gas-insulated transmission lines are not considered. This guide applies to ac transmission lines rated for maximum operating voltage of 72.5 kV and higher. The purpose of the tutorial is to provide technical assistance for the selection, application, and project management of GIL for transmission project, including decommissioning and retirement. It is not within the scope of the tutorial to address contractual or commercial questions related to GIL projects. The document includes tables, flowcharts and other aids that may be of use in a typical GIL project.