IN THE MINDS OF SOME, troubleshooting in buildings, particu larly with regard to moisture problems, conjures visions of investigators poking with flashlights in dark corners or dangling from ropes on a building wall hundreds of feet above the street. While troubleshooting may include the above secretive or heroic modes of operation, more frequently and more typically troubleshooting involves the preparation of test protocols, performance of diagnostic tests, and the careful evaluation of test results. Troubleshooting building problems is much like the work of the detective who tries to solve a crime or the doctor who attempts to diagnose and cure a patient's illness. The term building diagnostics has come into frequent use and certainly can be applied to moisture investigations. The term building diagnostics here refers to the use of tests providing measurable results for determining the performance of buildings and their components. Although standard test methods are usually applied, it can include the development of tests for a specific case, as standard methods do not exist for all the tests an investigator may wish or need to undertake. In some instances, the evaluation of test results is straightforward, consisting of a comparison with some standard or code value; in others, it includes an element of the investigator's experience in similar cases. However, moisture investigations include more than the conduct of tests and measurements. They include the gathering of physical evidence, surveys of damage, and occupant surveys. Finally, the approach of the investigator and the determination of what tests to perform, at what time, and under what circumstances are still largely an art, and no two investigators are likely to follow the same protocol in the same case. As standardized test methods become more abundant, as they are applied with greater frequency, and as the community of investigators becomes more aware of each others' work, moisture investigations also will become more standardized as generally accepted protocols are adopted.