SummaryA highly significant association was found between the bovine MHC class I antigen BoLA‐A8 and a form of vertebral osteophytosis/ankylosing spondylitis known as chronic posterior spinal paresis (PSP) in Holstein bulls (P<0.001). In a population study, restricted to unrelated bulls, BOLA‐A8 was significantly associated with PSP (P= 0.0015) with a relative risk of 34.6. In a family study, one PSP bull, BoLA A8/A20, sired 13 offspring. BOLA‐A8 was significantly associated with PSP (P= 0–0008). All five PSP sons inherited the A8 allele and the eight healthy sons each inherited the A20 allele. In three other families a complete association of BOLA‐A8 and PSP was observed. Lod score analysis, using all available families, indicated a significant linkage between BoLA and PSP (lod score = 6–9). Based on clinical observation, pathology, age/sex predilection, and a strong association with a class I MHC molecule, this inflammatory disease appears analogous to the human condition known as ankylosing