OBJECTIVE We analyzed a large number of stage I clear cell carcinoma of the ovary (CCC) patients to estimate the survival impact of the capsule status in stage I CCC patients, particularly in comparison with non-CCC patients. METHODS Clinicopathologic data on 564 patients with stage I epithelial ovarian cancer (EOC) collected under the central pathological review system were subjected to uni- and multivariable analyses to evaluate the disease-free survival (DFS) and overall survival (OS). RESULTS There was no significant difference in both the OS and DFS of CCC patients between IA and IC(ir) (intraoperative capsule rupture) {IA vs. IC(ir); OS: P=0.1402, DFS: P=0.2701}. In contrast, CCC patients at IC(non-ir) {IC excluding for IC(ir), such as preoperative capsule rupture, positive ascites/washing, and surface involvement} showed a poorer OS and DFS than those at IC(ir), or those at the corresponding stage in non-CCC. In multivariable analysis, the capsule status was an independent prognostic factor of a poor OS and DFS {OS: HR, 2.832; 95% CI 1.156-6.938; P=0.023; DFS: HR, 4.327; 95% CI, 1.937-9.667; P=0.0004)} {In contrast, non-CCC: N.S. (OS/DFS)}. Furthermore, in CCC patients, intraperitoneal recurrences were more frequently observed in IC(non-ir) CCC than IA or IC(ir) CCC (P=0.0083) {In contrast, non-CCC: N.S.}. CONCLUSIONS This study suggests that CCC patients other than those with intraoperative capsule rupture show a considerable risk for mortality despite adjuvant chemotherapy.