Non-secretion of ABO blood group substances in body fluids is associated with susceptibility to some bacterial infections. Non-secretors were previously found to be over-represented in patients with ankylosing spondylitis (AS) (49%) compared to controls (27%). Re-evaluation of secretor status in a population of 92 AS patients and 103 controls revealed identical proportions of non-secretors (28%). Of 43 patients studied in both surveys, 6/22 typed initially as non-secretors proved to be secretors using both haemagglutination inhibition assay (HAI) and enzyme-linked immunosorbent assay (ELISA) techniques. Loss of secreted blood group antigens in the saliva is the cause of this mis-typing. Careful attention to the method of collection, handling and preservation of saliva specimens is essential for accurate assessment of secretor status. Therefore, there is no link between secretor status and AS.