Inflammatory joint diseases are major causes of invalidity and morbidity. Rheumatoid arthritis (RA), the most frequent of chronic arthritides, affects close to 1% of the Canadian population. Direct and indirect costs of RA represent close to 1% of the gross national product. Recent evidence suggest that initiation of early (e.g., during the first 3-12 months of disease) aggressive treatment decreases both mortality and long term invalidity in RA and other chronic arthritides. However, a significant proportion of patients with early polyarthritis (EPA) have a benign evolution, even if they fulfill criteria for RA. On the contrary, most patients whose arthritis persist for more than 12 months have a progressive and destructive disease. Currently available clinical, serological and genetic markers of severity in arthritic patients perform poorly in EPA patients to identify those patients whose arthritis is likely to persist and thus who deserve an aggressive treatment. The Investigators propose a prospective and longitudinal study to define the contribution of detection of rheumatoid arthritis-specific autoantibodies (RASA), either alone or in combination with other markers of severity, in the prognostic evaluation of patients presenting with EPA. Availability of such an effective serological tool to establish prognosis in individual patients would improve therapeutic decisions in clinical practice. The same prognostic tools would represent very powerful instruments to subset patients into more homogeneous groups in clinical trials, increasing their power.