This study was performed to assess the clinical and diagnostic features of ankylosing spondylitis in Korean. One hundred and seventeen cases of ankylosing spondylitis treated at the Severance Hospital, Yonsei University College of Medicine from 1980 to 1992 were analyzed in clinical, radiological and labroatory aspects. The average age at diagnosis was 38 years (range: 14 to 79 years) and male (93%) was predominently involved. The average age at onset of disease was 26 years. The most frequent location of pain was low back (38.5%) and radiating pain occurred in 50.4% of the cases. The main stiff regions were hip joint (35.9%) and lumber spine (25.0%). Most frequently affected joint was hip (44.1%) and extraskeletal manifestations were pleuropulmonary disease (31.4%), gastrointestinal disorders (20.8%) and iritis (11.1%), etc. On laboratory tests, the erythrocyte sedimentation rate was increased (88.9%) and the HLA-B27 antigen has been found to be positive (97.7%). Rheumatoid factor was negative (96.8%) and the serum immunoglobulins (29.75) and complements (32.95) were increased. The characteristic radiologic findings were sacro-iliac changes (81.8%), facet joint blurring (60.0%) and syndesmophyte (29.9%). The S-I index (sacro-iliac/sacral uptake X 100) was calculated on quantitative scintigraphy and the mean indices of ankylosing spondylitis were significantly higher than the normal population (p<0.05, one way ANOVA). Our study indicated that the ankylosing spondylitis is characterized by the symptoms including extraskeletal manifestations. The HLA B-27 antigen, ESR and the radiologic features including quantitative scintigraphy of the sacroiliac joint were helpful to confirm the diagnosis of ankylosing spondylitis.