Hypersensitivity Lung Disease (HLD) includes Hypersensitivity Pneumonitis (HP), IgE triggered asthma and Allergic Bronchopulmonary Aspergillosis (ABPA). HP and ABPA are neither common nor rare. Both are important to diagnose as they can result in progressive irreversible lung damage. Serologic tests are useful in diagnosing or excluding HP and ABPA although the diagnostic skill of the physician is of prime importance. We report eight cases which were diagnostic problems in which the initial serologic examinations were incorrect. The diagnostician must be aware of both the clinical possibility of the HLD but also of the possibility or probability that the serologic report is not correct.