Historically, silicones have been considered biologically inert materials, and have therefore been used widely in a variety of medical applications. Recently, controversy has arisen concerning the bioreactivity of silicone; reports of adverse inflammatory and immunological complications that may be evoked by silicone breast implants have appeared in the medical literature and have received great attention from the lay press. The phenomena said to be associated with silicones may be attributed pathophysiologically to the inherent surface activity of silicone. The human body's initial response to the silicone of breast implants is the adsorption of various plasma proteins, including clotting and complement proteins, to the implant surface. Other macromolecules in the biological milieu may follow. The conformational integrity of this adsorbed macromolecular layer affects much of the subsequent biological reaction. Clinically silent inflammation, locally significant inflammation, inflammation with constitutional symptoms, and inflammation with immunological activation are possible consequences.