This test method provides a procedure@ which is suited for determining the relative degree of crosslinking of polymeric@ electric cable insulations. Summary of Method: Elongation Test: A specimen is subjected to a constant load stress while suspended in an air oven at a specified elevated temperature for a specified time period. At the end of the time period the increase in elongation of the specimen is determined. Set Test: Immediately after the elongation test has been completed on a specimen@ the same specimen with the load stress removed@ will be subjected to an additional time period in the oven at the same elevated temperature. The specimen is then removed and allowed to cool. The set of the specimen@ based on original length@ is then determined. Significance: The test method has a consistent reproducibility@ which makes it particularly suitable as a quality control test for determining relative degree of crosslinking. This method has been found more reproducible than the other methods in current use such as heat deformation. Also@ it corresponds more closely to service conditions than a solvent-extraction procedure.