Behçet's disease (BD) is a chronic inflammatory condition involving several organs, such as skin, mucous membrane, eye, joint, intestine, lung and central nervous system. Ankylosing spondylitis (AS) is a prototype of seronegative spondyloarthropathy, and a chronic systemic inflammatory disorder of the axial skeleton, mainly affecting the sacroiliac joint and spine. In the latter, systemic complications may develop in addition to joint involvement. The coexistence of BD and AS has been rarely reported in the literature. The inclusion of BD among seronegative spondyloarthritides and whether sacroiliitis (SI) develops in BD are still being debated. We describe a 28-year-old man who has fulfilled the diagnostic criteria for BD and AS as well.