Increased awareness and sensitivity of general physicians have increased the early diagnoses of seronegative arthritis in young patients, while new agents such as anti-TNF blockers have significantly changed the treatment of the disease. To investigate the prevalence, the clinical manifestations, and the ability for military service of young Greek males (18-30 years old) with ankylosing spondylitis (AS) in the pre-anti-TNF era. We retrospectively studied the AS cases recorded from 1989 to 1995 of the rheumatology department of the largest General Military Hospital in Greece; the diagnosis was based on the modified New York criteria for AS. A total of 285 AS cases were diagnosed among 357,184 young men. The overall prevalence of AS on December 1995 was estimated at 8.2 cases per 10,000 young men (95 % C.I. 7.2-9.2). All the patients had chronic back pain. Two hundred forty (84 %, 95 % C.I. 79-88 %) patients presented sacroiliitis of whom 163 (68 %, 95 % C.I. 62-73 %) were bilateral. Two hundred five patients (72 %, 95 % C.I. 66-77 %) had peripheral joint involvement. Thirty-one patients presented with anterior uveitis (11 %, 95 % C.I. 8-15 %). One patient had IgA nephropathy. None had gut involvement. HLA-B27 antigen was found in 257 patients (90 %, 95 % C.I. 86-93 %). Ninety-one patients (32 %, 95 % C.I. 27-38 %) had permanent discharge from the military service, while 128 (45 %, 95 % C.I. 39-51 %) were able for auxiliaries attendances. The prevalence of AS for the age group 18-30 years old in this young Greek men cohort was significantly lower than in other Caucasian European populations, and the clinical manifestations were considered as mild.