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.