An insertion mutation at nucleotide 3020 (3020insC) and a missense mutation G2722C in the CARD15 gene on chromosome 16p have been reported to be associated with Crohn's disease (CD). The protein encoded by the CARD15 gene is expressed in peripheral monocytes and regulates apoptosis and NF-kappaB activation, factors which play an important role in inflammation. Since CD and ankylosing spondylitis (AS) are interrelated disorders, we have investigated whether these mutations in the CARD15 gene are also associated with AS. We studied 113 unrelated AS patients and 152 unrelated healthy controls. No significant differences were found between patients and controls in the prevalence of the insertion 3020insC mutation and the G2722C missense mutation, OR = 1.36, 95% CI: 0.27-6.84, P = 0.70 and OR = 0.58; 95% CI: 0.18-1.94; P = 0.38, respectively. We conclude that the insertion 3020insC mutation and the G2722C missense mutation in the CARD15 gene are not involved in the susceptibility to AS.