Background: Ankylosing spondylitis (AS) is an inflammatory disease that affects the spine and sacroiliac joints and is connected with the human leukocyte antigen (HLA)-B27. Late-onset AS is characterized by severedisease-marked elevation of laboratory measurements of inflammation, and more frequent involvement of the peripheral joints and the cervical spine as compared with early-onset ASObjective:This topic aimed to study the clinical, radiological, and biological profile of Algerian patients presenting Late-Onset Ankylosing Spondylitis in comparison with patientswith Early-Onset Ankylosing Spondylitis.Methods: 292 patients diagnosed with AS at the level of rehabilitation department of Hassani AEK hospital of Sidi bel abbes region were enrolled. Studied parameters were: age, disease duration, morning stiffness, joint involvements, laboratory data, disease activity, and treatments.  All data were processed and analyzed via SPSS 20.0 (Statistical Package for the Social Sciences, IBM Corporation, Chicago, IL August 2011). Results: A total of 247 patients had early-onset AS, while 45 had late-onset AS. The Age Onset Ankylosing Spondylitis was associated significantly with age and disease duration p<0.0001, the average mean duration morning stiffnesswas higher in a group of late-onset age 8.00±0.000 years VS 6.91±4.288 years. However, acute inflammation was more noted in theLoAS group (93.3% Accelerated ESR and 60% positive CRP) and 93.3% of positive HLAB27 was noted in this late group with p=0. 049. Whereas, the group of early-onset age suffered more from their cervical 40.4% and lumbar 74.4% and,  theywere the most affected in their peripheral joints (knees affection 14.1% vs 0% and hips affection   32.9% vs 6.7 %, p=0.033). Furthermore, high disease activity indices were more noted in this young group (BASDAI 2.984±1.942 VS 2.194±0.774 and ASDASCRP 2.659±1.309VS 2.106±1.091). Uveitis (AAU) was the most common comorbidity reported in both groups and the Sulfasalazine and Humira treatment was the most received in each group but the methotrexate treatment was more used by the early-onset AS p=0.038.Conclusion: In our study, the late-onset group exhibits higher levels of inflammation and more positive HLAB27 than the early group, which was more affected by extra-articular damage, lumbar pain, and peripheral joints. The late and early age onset groups had different AS characteristics.