To clarify the optimal timing of second look operation (SLO) for advanced ovarian cancer, we retrospectively reviewed the records of 53 patients with FIGO stage 2, 3 and 4 epithelial ovarian cancer. SLOs were performed more than 12 months after primary surgery in 35 patients (late SLOs), and immediately after first-line chemotherapy in 18 patients (early SLOs). We examined data on SLO findings and patients' clinical courses. SLO findings were positive 5 (27.7%) of 18 in the early SLO group and in 11 (31.4%) of 35 in late SLO group. Positive findings were detected by washing cytology in 3 (60%) of the 5 in the early SLO group compared with 2 (18.2%) of the 11 in the late SLO group. Patients with microscopic disease had better prognosis than patients with macro lesions. False-negative SLO findings were 30.8% in the early SLO group and 12.5% in the late SLO group. All patients who recurred after negative SLOs had grade 2 and 3 tumors. The benefits of SLO were limited to accurate evaluation of first-line chemotherapy and early detection of persistent disease. In these implications, early performance of SLO is recommended.