The incidence of Lyme disease is increasing. This spirochetal infection may frequently manifest itself with joint involvement without characteristic dermatologic signs or history of tick bite. Serologic testing remains unreliable. Oral or parenteral antibiotics remain the mainstay of treatment. Chronic arthritis develops in approximately 10% of patients with Stage III disease. Lyme arthritis must be considered in the differential diagnosis of patients with mono- or oligoarticular joint involvement, especially in children and young adults with possible tick exposure. Further advances in antimicrobial therapy and serologic testing are anticipated.