This chapter explores that the issues of Multiple Chemical Sensitivity (MCS) has occasionally been raised in relationship to exposures which occur in industrial and office workplace environments. MCS has been described as an acquired disorder characterized by recurrent symptoms affecting multiple organs, symptoms which occur as a result of exposure to many unrelated compounds at doses far below those reported to cause harmful effects. MCS symptoms are suggested to be elicited by exposures to diverse chemical structural classes and toxicological modes of action at exposure levels lower than 1% of established threshold limit values. Systematic studies are required to take the phenomenon of problem/sick buildings from an initial identification stage based on field investigations to the level of good science. Sick building syndrome (SBS) is used to describe a diffuse spectrum of symptoms in which no specific etiological factor can be identified. A variety of organizations have attempted to define SBS and sick buildings.