PURPOSE: This study evaluated the clinical presentations of Staphylococcus epidermidis (S. epidermidis) septic arthritis after arthroscopic anterior cruciate ligament reconstruction (ACLR). MATERIALS AND METHODS: Between September 2006 and February 2008, S. epidermidis septic arthritis developed in six patients following arthroscopic ACLR. We reviewed the medical records retrospectively and interviewed the patients. RESULTS: The average interval between ACLR and symptom onset was 4.7 days (range, 2 to 8 days). Local warmth, swelling limited knee motion and general malaise were observed in varying degrees in all the patients. The fever was generally slight with an intermittent spiking pattern. Postoperative erythrocyte sedimentation rate and C-reactive protein were elevated. After the development of infection, the joint was aspirated in all cases. The white blood cell count was at least 22,400, with the presence of 80 to 90% of polymorphonuclear cells. All the patients had a few Gram-positive cocci and positive cultures for S. epidermidis. CONCLUSIONS: The symptoms, signs and laboratory findings of S. epidermidis septic arthritis following ACLR are nonspecific with various clinical presentations. So the diagnosis is often delayed. Positive gram staining can be used to confirm septic arthritis. Careful observation for septic arthritis is advised in case of presence of any abnormality after ACLR.