BACKGROUND It is controversial whether patients with stage I ovarian clear cell carcinoma (CCC) benefit from postoperative chemotherapy. This study was designed to evaluate the postoperative outcomes associated with the inclusion or exclusion of adjuvant therapy in these patients. METHODS A total of 185 patients who were treated for stage I CCC between 1991 and 2007 were retrospectively evaluated. All of the patients had received comprehensive surgical staging, and their condition had been diagnosed by a central pathological review system. Only one patient with stage IB was excluded from this study. RESULTS Median follow-up time was 62 months (range 7-191 months). Median age was 52 years (30-75 years). There were 41, 93, and 50 patients in stage IA, intraoperative capsule ruptured IC (rupture-IC), and all other-IC groups, respectively. The 5-year recurrence-free survival rates for the substage were 97.6%, 87.8%, and 70.4% (P < 0.001), respectively. Among 134 patients consisting of those in the stage IA and rupture-IC groups, 91 patients received adjuvant chemotherapy (AC) and 43 patients did not (non-AC). There was no significant survival difference in each substage group between the non-AC and AC groups in 5-year recurrence-free survival rate (stage IA, 100% vs 93.8%; rupture-IC, 94.1% vs 86.6%). Multivariate analysis demonstrated that there was no significant prognostic factor for both recurrence and survival among the IA and rupture-IC groups. Postoperative therapy, regimen, and chemotherapy cycles were not significantly affected. CONCLUSIONS This study indicates that adjuvant chemotherapy does not contribute to the improving prognosis of stage IA ovarian CCC. Whereas the histological type is CCC, the routine adjuvant chemotherapy after comprehensive surgical staging may be unnecessary for patients with at least stage IA.