In 1982, 3370 cases of inflammatory rheumatism were declared. The geographical analysis of the distribution of these cases (departmental and regional) suggests that their distribution is not homogeneous throughout the country, with a predominance of psoriatic arthritis in the Midi and the Pyrenees and a predominance of rheumatic pelvispondylitis in Aquitaine. Based on the number of cases declared, we can calculate the distribution of each type of inflammatory rheumatism by age and by sex and the incidence per million inhabitants in each age group. These figures are only indicative, as the data from some departments was incomplete. The calculation of a "criterion of frequency" attempts to equalize this bias. Reactive arthritis (352 cases) represents 10.4 p. cent of all cases of inflammatory rheumatism. This large series collected over one year confirms the clinical data already established. The responsible organisms, by order of frequency, were: Chlamydia trachomatis, Yersinia enterocolitica, Shigella, Y. pseudotuberculosis and Ureaplasma urealyticum. 50 p. cent of these cases of arthritis were classified as reactive on the basis of clinical findings and history and the bacteria was not isolated. The HLA-B27 antigen is present in 68 p. cent of the 302 cases in which it was tested.