Innate immunity recognizes invading micro-organisms and triggers a host defence response. However, the molecular mechanism for innate immune recognition was unclear. Recently, a family of Toll-like receptors (TLRs) was identified, and crucial roles for these receptors in the recognition of microbial components have been elucidated. The TLR family consists of 10 members and will be expanding. Each TLR distinguishes between specific patterns of microbial components to provoke innate immune responses. The activation of innate immunity then leads to the development of antigen-specific adaptive immunity. Thus, TLRs control both innate and adaptive immune responses.