Axial spondyloarthritis (axSpA) is an inflammatory joint disease, in which the dominant symptom is inflammatory back pain. It affects approximately 1% of the population, with a higher incidence in males. Spinal pain associated with spondyloarthritis is referred to as inflammatory back pain. In clinical practice, it is extremely important to be able to assess the activity of inflammatory back diseases and to select appropriate treatment and monitor the therapy. Currently, two main tools are used for assessment of the activity of axial spondyloarthritis: BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) and ASDAS (Ankylosing Spondylitis Disease Activity Score). The BASDAI is a tool used for years for assessment of disease activity, determining eligibility for treatment, and making decisions about continuation of therapy. Since BASDAI depends entirely on patient self-assessment, it is considered less objective than the ASDAS index. In turn, the latter includes not only answers to questions provided by the patient but also a parameter of inflammation such as erythrocyte sedimentation rate or C-reactive protein (CRP). Additionally, increasing numbers of studies report advantages of the ASDAS index over BASDAI. Moreover, as indicated by ASAS/EULAR (Assessment in Spondyloarthritis International Society/European Alliance of Associations for Rheumatology) 2022, ASDAS, especially ASDAS-CRP is the preferred tool for assessment of the activity of axSpA, whereas BASDAI is used only when the evaluation of the ASDAS is not possible. This paper presents the definition and symptoms of axSpA and reviews the latest research on ASDAS and BASDAI, with emphasis on the objectivity of the ASDAS assessment also presenting the doubts and limitations concerning this tool.