This study aimed to develop a simplified version of the Ankylosing Spondylitis Disease Activity Score (ASDAS). The study included consecutive patients with ankylosing spondylitis according to modified New York and/or Assessment in Ankylosing Spondylitis 2009 criteria. Sociodemographic data and characteristics of the disease (Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Ankylosing Spondylitis Quality of Life (ASQoL)) and erythrocyte sedimentation rate (ESR) were collected. ASDAS simplified version (SASDAS) was calculated as the simple linear sum of the five components of ASDAS which include: patient global assessment using visual analogue scale, back pain (BASDAI question no. 2), peripheral pain and swelling (BASDAI question no. 3), morning stiffness (BASDAI question no. 6), and ESR in millimeters per hour, divided by 10 so as to make it equivalent to the other scale's components. Eighty-six patients were included: 69 (80.2 %) were men with a median age of 46 years and median disease duration of 19 years. SASDAS showed an excellent correlation with the ASDAS (r = 0.93). SASDAS also showed a good correlation with night pain (r = 0.60), global pain (r = 0.69), ASQoL (r = 0.70), BASFI (r = 0.75), and BASDAI (r = 0.96). Using ASDAS cut-off values previously suggested, the corresponding cut-off values for SASDAS were as follows: from 0 to 7.8 (inactive disease), from 7.9 to 13.8 (moderate disease activity), from 13.9 to 27.6 (high disease activity), and above 27.6 (very high disease activity) with optimum sensitivity and specificity. SASDAS showed an excellent correlation with conventional clinical measures of disease activity, and it can be easily calculated and is simple to use in daily clinical practice.