OBJECTIVE: The purpose of this study is to find out the differences of clinical characteristics of endometriosis and to emphasize the significance of early diagnosis of endometriosis to protect disease progression in adolescents. METHODS: A retrospective analysis was carried out. All cases (n=130) were diagnosed surgically as endometriosis between January 2000 and August 2007 in two university hospitals in Daegu. Adolescents were 23 cases and unmarried young women were 107 cases. Data were collected through review of medical records. RESULTS: The predominant symptom in adolescents was cyclic pain. 52.2% of adolescent patients were stage I or II. And stage III was 47.8% but stage IV was none. The other side 82.2% of unmarried young women patients were stage II or III and stage IV was 15.8%. Serum CA-125 level was elevated in adolescnets, also. But there was no significant difference between the two groups. CONCLUSIONS: Endometriosis is progressive disease. Early diagnosis is necessary for prevention of the disease progression and free from pain. Appropriate gynecologic examination and careful concerns about adolescents are mandatory.