Reactive arthritis (ReA) was known as Reiter's disease or Fiessinger-Leroy disease for nearly 100 years. However, during the past 30 years the disease has been known as reactive arthritis, a member of the spondyloarthritis family. Despite knowing the initiating event (infection) and genetic constitution (many patients have HLA-B27) of ReA, a model of interplay between environment and genetics, its pathogenesis is still incompletely known. This review covers the epidemiology, clinical features, treatment, and prognosis of ReA.