Two cases of the association of monoclonal IgM and ankylosing spondylitis are reported. Their presentations are in accordance with local epidemiological data (monoclonal IgM, both kappa, one of them malignant, discovered in 71 and 79 year-old men). Ankylosing spondylitis does not appear as either favouring the incidence of monoclonal immunoglobulins or, in our opinion, having a major influence on their isotype. Conversely, while each member of this association could have its own story, the possible role of the coexistence of HLA B27 together with ankylosing spondylitis should be considered.