The classification of Spondyloarthritis (SpA) has been revised with the introduction of the ASAS classification criteria. Although this has best been described in ankylosing spondylitis and psoriatic arthritis, there are population studies evaluating the epidemiology of the different subgroups of SpA. In this paper, we present data on the incidence and prevalence of the subgroups of SpA in different populations, and point to data indicating how the introduction of new classification criteria, with the altered perception of the SpA entity, might impact on the epidemiology.