The concept of airway hyperreactivity is important for a full understanding of pulmonary disease from the pharmacological, toxicological and clinical viewpoint.

The review defines bronchial hyperreactivity and presents a general introduction to the concepts of hyperreactivity and hyperresponsiveness. This is then related to the concept of clinical disease states. Some of the methods used in the diagnosis and monitoring of respiratory disease are also considered together with the tests used to measure changes in reactivity which have been either inbred or induced in laboratory animals.

Hyperreactivity is then considered under three convenient categories:

a) Genetically determined, b) Immunologically induced, c) Non - immunologically induced.

Various animal models for the above categories are discussed and wherever possible the relationship between animal model and human disease is considered along with the strengths and weaknesses of given models. The category of non - immunologicallyinduced hyperreactivity is examined in more depth as being of greater relevance to byssinosis. Examples of 'irritant` substances that induce hyperreactivity and alteration of lung function are presented and the proposed mechanisms by which some 'irritants` induce hyperreactivity are also considered.

Finally the question is posed as to whether there is a common link or mechanism between the various types of hyperreactivity and proposals for the direction of future research are made. In examining directions of further research two aspects form a main focus: i) elucidation of detailed mechanisms of induction and ii) genetic information, although many other areas are equally important in making progress towards improving the treatment of disease.