This chapter discusses ankylosing spondylitis and other seronegative spondyloarthropathies. Spondyloarthropathy (SpA) is the name for a family of chronic inflammatory rheumatic diseases that causes progressive arthritis often predominantly involving the sacroiliac (SI) joints and the spinal column. SpA is a chronic, multisystem inflammatory disorder involving primarily the SI joints and the axial skeleton. The most common spondyloarthritis is ankylosing spondylitis (AS) which affects mainly the spine. There are other well-known spondyloarthropathies. Ankylosing spondylitis is the prototype of the spondyloarthropathies presenting with inflammation of the axial skeleton, peripheral arthritis, and enthesitis. Types of seronegative spondyloarthropathies, clinical features, medical or nonsurgical treatment, juvenile ankylosing spondylitis, pharmacologic therapy in ankylosing spondylitis, surgical treatment, and mortality/morbidity are also discussed in this chapter.