Corrosion is a major factor affecting the selection, efficiency and safety of many processes operating at elevated temperatures. This is particularly the case in coal gasification plant where a number of contaminants derived from the coal feedstock can cause severe degradation through corrosive attack. Testing of materials for inclusion in such plant can be undertaken eitherin situor in the laboratory under simulated plant conditions. The latter method is commonly used owing to the need to establish, in a controlled manner, the mechanisms governing the mode and rate of the corrosion degradation processes. The paper describes the development of laboratory test methodologies that simulate specific elements of corrosion processes occurring under real plant conditions, allowing predictive models for materials behaviour to be developed. An important aspect of the laboratory studies is the development of test methodologies that permit close control of experimental parameters and have the capability of being reproduced not only in the same laboratory but in other laboratories. Fully reproducible test methodologies could eventually be used as standards. If accepted standard test methods for obtaining commercially relevant data can eventually be established, the database for candidate and new materials should grow and, as a result, better provide for future plant design and operating requirements.