After developement of antimicrobial chemotherapy, morbidity and mortality from pyogenic arthritis has been reduced dramatically, but still this disease has remained as a serious and lifethreatening infectious disease of childhood or late sequelae in surviving patients. For the period of 7 years from January 1973 to December 1979, fifty nine children who were treated as septic arthritis at Severance Hospital were studied retrospectively and the results are summerized as follows. 1. Among the 59 cases, 32 cases (54.25%) were male and 27 cases (45.8%) were female. The most prevalent age was 4 to 10 years (40%). 2. Lag period to treatment in most cases was 5 days, and the most prevalent signs on admission was pain around the involved joint. 3. The most commonly affected joint was the hip joint (42.4%). The other affected sites in order of frequency were the knee, ankle and shoulder joint. 4. The underlying causes were composed of infectious focus in 18 cases, minor trauma in 6 cases, iatrogenic reason in 4 cases and unknown in 31 cases. 5. In laboratory findings, the numbers of W.B.C. and E.S.R. were increased in 66.1%, and roentgenologic studies revealed normal in 67.7%, soft tissue swelling in 21% and joint space widening in 9.7%. 6. Causative micro-organism was isolated in 41 cases: Staphylococcus aureus in 34 cases. B-hemolytic streptococcus in 3, Pseudomonas aeroginosa in 2, Enterobacter species in 2. 7. Staphylococcus aureus was highly sensitive to Cephalothin (88.2%) and Methycillin (85.3%), but was highly resistant to Penicillin (88.2%). 8, Four cases were treated non-surgically and 55 cases surgically with arthrotomy-drainage and arthrotomy-continuous irrigation. The results were satisfactory in 83% and unsatisfactory in 17%. 9. The complications were found in 14 cases: recurrence in 4, joint stiffness in 3, dislocation in 2 and sepsis in 1 case. In conclusion, a better result was obtained in cases with early diagnosis and surgical treatment with proper antibiotics.