In this review, recent data relevant to better understanding of the immunogenetics of the spondyloarthropathies are discussed or, in a somewhat broader sense, the HLA-B27 disease associations. Although in 1993 much more is known about the B27 molecule than was known in 1992, its contribution to the pathogenesis of disease is unclear. Peptide presentation to the T-cell receptor is still the basic, if not the only, function of HLA class I molecules. Nothing special was found for the B27 gene, molecule assembly, protein sequence, and crystal and peptide-binding motif, nor for the function dependent on these physical properties. Nevertheless, the theory regarding an "arthritogenic peptide" seemed to promise an explanation. However, this theory is rather an assembly of older views modified by the new data and is missing any detail or perspective that would answer the specific question: why B27 and not other HLA molecule(s)? If the solution is simple, and B27 is qualified to bind certain (bacterial) peptides that are not bound by any other class I molecule, or the unique complex, B27 + x, has special properties resulting in a "dysfunction," there is still no answer to the question: which peptide and why does its binding with B27 result in disease?