Ankylosing spondylitis affects 0.1%-0.5% of the adult population. The aim was to investigate the possible effects of both the disease and its treatment on semen quality by performing a highly detailed analysis in a man with ankylosing spondylitis, presenting for infertility. Sperm characteristics were evaluated by light microscopy, morphology by electron microscopy (transmission electron microscopy), DNA fragmentation by terminal deoxynucleotidyl transferase dUTP nick end labeling using fluorescence microscopy and chromosomal abnormalities by fluorescence in situ hybridisation using probes for chromosomes 13,15,16,18,21,22,X and Y. There was no evidence for an effect of either ankylosing spondylitis or its treatment with celecoxib and sulphasalazine on sperm quality as all parameters including concentration, motility, DNA fragmentation and aneuploidy incidence were within normal limits. Transmission electron microscopy, however, revealed a high incidence of head, neck and tail abnormalities, as well as the presence of immature sperm and phagocytes. Hysteroscopic removal of an endometrial polyp enabled the achievement of a spontaneous pregnancy and the delivery of a healthy boy.