Isolated monoarthritis caused by Mycobacterium tuberculosis in the absence of clinical pulmonary disease is extremely rare in North America. After decades of consistent declines in incidence, a remarkable resurgence of tuberculosis (TB) is occurring in North America. It must always be considered in the differential diagnosis of chronic monoarthritis if devastating sequelae are to be avoided. We describe 2 cases of tuberculous arthritis in young children presenting with monoarthritis of the knee. The presumptive diagnosis in each case was oligoarticular onset juvenile rheumatoid arthritis (JRA). Each had an atypical course for JRA, with lack of response to intraarticular corticosteroid. The diagnosis of TB arthritis was made only with synovial biopsy.