The occurrence of arthritis in patients who were infected by a virus has been widely observed. In some cases, the clinical appearance seems to resemble that of rheumatoid arthritis. The mechanism by which the viral infection proceeds to the arthritic manifestation is, however, still to be investigated. Several biological and immunological pathways are suggested to be involved in the pathogenesis. The representatives of such potentially 'arthritogenic' viruses include human T-cell lymphotropic virus type I (HTLV-I), which causes destructive inflammatory arthritis in model animals. Other examples are hepatitis C virus and rubella virus. Clinical and pathological features of these virus-induced forms of arthritis are discussed.