Ankylosing spondylitis (AS) is a chronic, progressive, and disabling disease. Among the rheumatological diseases, the longest diagnosis delay is still found for AS. The aim of this cross-sectional study is to evaluate the diagnosis delay and possible reasons in AS. A secondary aim is to assess the relation between diagnosis delay and some clinical and laboratory features. One hundred eleven AS patients, (103 male, 8 female) were recruited. A face-to-face interview was applied to take medical history, and a questionnaire that contains some clinical aspects of disease was used. Diagnosis delay was described as the gap between first spondiloarthropathic symptom and correct diagnosis of AS. The average of diagnosis delay was 6.05 +/- 5.08 years. The average age of patients at disease onset was 23.18 +/- 9.59, the average disease duration was 10.44 +/- 8.11, and the average age at diagnosis was 27.88 +/- 11.63. The average diagnosis delay was 5. 3 +/- 3.5 in HLA B 27(+) AS patients, whereas it was 9.2 +/- 7.7 in HLA B 27(-) AS patients (p = 0.037). Diagnosis delay in patients with inflammatory back pain (+) (IBP) at disease onset was lower than IBP (-) patients (3.28 +/- 3.32, 8.57 +/- 8.54; respectively) (p = 0.001). The patients having positive family history had lower diagnosis delay than those with negative family history (4.60 +/- 4.44, 10.00 +/- 2.30; respectively) (p = 0.003). The diagnosis delay is a challenge and an important problem for patients with AS and physicians. HLA B27 and family history should be considered while making new criteria. Inflammatory back pain should be emphasized as the main screening criterion for primary care physicians. These clinical and laboratory features had positive effect on the average diagnosis delay in AS patients. Describing new diagnostic criteria, which is more useful to diagnosis of AS, is necessary.