This review provides a clear explanation of the current status of two common airborne contaminants, lipopolysaccharide and (1-->3)-beta-D-glucan, in the induction of indoor air-related disease. A full description of the origin of these two products is given together with information of their structure and function. Details of the biochemical mechanisms by which they interact with human cells and the physiological consequences of these interactions are outlined. Both compounds play a key role in the induction of airway inflammation and this paper highlights the environmental importance in the work place and home of these inhaled agents in terms of respiratory disease.