Paper describes the special test equipment developed for evaluating the elevated temperature leakage performance of gaskets. Early results indicate that an elevated temperature test must be run over a period of days or weeks in order for the time/temperature effects to be meaningful. The objective was therefore to develop test methods which would permit the aging of a test gasket in a Kiln for as long as desired before being evaluated for tightness. Results of leakage tests on asbestos and non-asbestos rubber-bound sheet gasket materials are presented. They indicate that the aged hot tightness tests (named AHOT) are effective and offer many possibilities including long term aging at temperatures beyond the limits of the tightness test machine. These tests are therefore suitable as means to confirm elevated temperature gasket performance estimates from screening tests.