This article elucidates the prevalence and pathogenic roles of the MHC and microbial infections and clinical features and treatment of SpA across different populations from the arctic and subarctic regions to Central America, Asia, and Africa. Preliminary evidence suggests significant genetic and environmental influences on the onset and presentation of SpA, particularly AS, in these populations, which are different than those reported in white Caucasians; however, community surveys and longitudinal and case control studies are difficult to undertake in many of the developing countries. Thus, most of the currently available data have been devised from short-term and retrospective studies and should be treated with caution. Differences in referral and follow-up practices and the availability of rheumatology expertise and relevant resources may explain some of the differences observed in the populations discussed in this article. Furthermore, widely accepted criteria for the classification of SpA may not be applicable to non-Caucasians and need to be evaluated in these subjects. With gradual improvement in the economic status in many of the developing countries in Asia and Africa, it is hoped that with improvement in medical services, more physicians and specialty clinics in rheumatology, and changing referral patterns, better documentation of the various aspects of different SpA can be achieved. Future research should focus on the evaluation of specific risk or protective factors in population groups to better delineate the relative importance of genetic and environmental effects in the pathogenesis of SpA.