In a Yupik Eskimo population, the prevalence, incidence and clinical features of rheumatoid arthritis (RA) were similar to those described for the United States population in general. More frequent than RA were seronegative spondyloarthropathic disorders, many of which could not be classified by existing disease criteria. Of the adult patients with spondyloarthropathy only half could be classified as having Reiter's syndrome (RS), ankylosing spondylitis (AS) or psoriatic spondylitis. The remaining patients had many signs and symptoms consistent with spondyloarthropathy, but they either did not meet the diagnostic criteria for any specific disease or had features pathognomonic of more than one. The clinical manifestations of the patients who did not meet standard disease definitions are summarized and compared to those of the patients with RS, AS and psoriatic spondylitis. Because of the many shared features, we believe that these as yet unclassified disease states belong with AS and RS in a single spondyloarthropathic disease spectrum and should be defined and recognized as such.