Although many AS patients respond very well to anti-TNF therapy, a considerable amount of them do not and additionally a significant proportion of patients have to stop their treatment. In clinical practice the reported 1-year and 2-year drug survival rates for anti-TNF agents are 70-85% and 60-75%, respectively.Moreover in a substantial proportion of patients either increase in the administered dosage or dosing frequency have become necessary. Therefore factors, which can predict the response or related with the primary or secondary non-response for anti-TNF treatment have a growing attention among treating specialists. In a study providing an overview of clinical trials and observational studies showed that increased acute phase reactants, higher disease activity, functional status, younger age, and HLA-B27 positivity were independent baseline predictors of response to anti-TNF treatment and increased acute phase reactants, presence of peripheral arthritis, and male sex were the predictors of long-term drug survival.