Rheumatoid arthritis (RA) and spondylarthropathies are the most frequent chronic inflammatory arthritides. RA is a potentially severe disease which causes a functional handicap in nearly half the patients 10 years after the first clinical symptoms. However RA is a heterogenous disorder characterized by wide variations in clinical manifestations, disease course and response to therapy. No prognosis factor has been identified and universally accepted and validated. Markers of prognosis would be highly appreciated by clinicians who could then more closely adapt their management decisions to the disease potential. Clinical and biological data collected to date have provided a limited amount of information. Nevertheless, ESR, CRP and rheumatoid factor titer appeared to be the most powerful available indicators of prognosis at the early stage of the disease. Recent progress in molecular biology strongly suggests that genetic markers (HLA-DRB1 alleles) could be correlated with disease severity and it would appear possible to distinguish immunogenetically homogeneous subpopulations of patients with RA. Serum concentrations of specific cartilage and bone molecules reflecting tissue turnover could correlate to rate of joint destruction. Finally a combination of the most pertinent markers could determine a "score of severity" of the disease. In spondylarthropathies, limited information is available at present. The variables which were usually correlated with disease severity are: onset before 16 years of age, hip arthritis, ESR, limitation of lumbar spine, sausage-like finger or toe, oligoarthritis, poor efficacy of nonsteroidal antiinflammatory drugs and rapid evolution during the first 2 years. Genetic factors could also have prognosis value that should be clarified.