Behçet's disease (BD) is a multisystemic disorder characterized by oral, genital ulcers and involvement of the cutaneous (erythema nodosum, pustular vasculitis), ocular (anterior or posterior uveitis), musculoskeletal, vascular (both arterial and venous vasculitis), gastrointestinal and central nervous (meningoencephalitis) systems. It has an unpredictable clinical spectrum from mild mucocutaneous manifestations to severe ocular, vascular or neurological disability. In this review, the aetiology, clinical presentations and treatment modalities of BD are evaluated in the context of microbial factors within the existing literature. The relationships between microbial agents (streptococcia and herpes simplex virus), microbial antigens [heat shock proteins (HSP), lipoteichoic acid (LTA)] and immune mechanisms such as innate and adaptive responses against microorganisms are discussed. © Copyright Clinical and Experimental Rheumatology 2007.