With the revision of AIEE Standard No. 1 a few years ago when the insulation systems concept was formalized, many AIEE committees developed test codes for the evaluation of systems of insulation for the types of apparatus within their scope. The new standard has recognized that the suitability of an insulation system, aside from significant thermal consideration, is influenced by the manufacturing techniques and processes of construction as well as the exposure of the apparatus in service to electrical and mechanical stress, vibration, moisture, chemicals, etc. Basically, what was needed was an accelerated life test, and it is the intent herein to develop an accelerated life test procedure which embodies the various factors known to affect insulation life. By subjecting a known or proven insulation system to this test procedure, data will be collected which can be projected to an equivalent life, thus enabling a designer to compare a new insulation system with the established one.