Fifteen cases of ankylosing spondylarthritis, associated to an IgA nephropathy have been reported in the literature. This association may be fortuitous, or on the contrary suggest a common pathogenic link between the two diseases and the authors have compared the incidence of radiological abnormalities of the sacro-iliac joints as well as the incidence of rheumatoid clinical signs in 186 patients suffering from an IgA nephropathy to those observed in 192 reference patients. This study could not demonstrate any difference between the two groups and, therefore, suggests that the cases reported in the literature are secondary to a simple fortuitous association.