OBJECTIVE: To assess the use of colony-stimulating factors (CSFs) in patients with ovarian cancer who receive adjuvant paclitaxel and carboplatin chemotherapy in clinical practice and to assess whether the frequency of CSF use differs among hospitals in Japan. METHODS: CSF use in patients with ovarian cancer who received first-line paclitaxel and carboplatin was analyzed retrospectively using data from the Japanese hospitalization payment system. RESULTS: A total of 1,050 patients at 104 hospitals were identified. The median age was 60 years (range, 22 to 88 years). Of these, 163 patients (15.5%) were diagnosed with neutropenia and 134 patients (12.8%) received CSFs. Among the patients who received CSFs, 125 (93%) received them for the treatment of neutropenia without fever and 1 received them for febrile neutropenia. In total, CSFs were administered for 272 cycles of chemotherapy. Among them, CSFs were used as treatment for neutropenia without fever in 259 cycles (95%), as prophylaxis (primary or secondary) in 12 cycles (4%), and as treatment for febrile neutropenia in 1 cycle. Among hospitals, a median of 4.0% of patients received CSFs with an interquartile range of 25% (Q1, 0%; Q3, 25%). A logistic random effects model showed that the variation in the proportion of patients receiving CSFs among the 104 hospitals was 2.0 (p<0.001), suggesting that the use of CSFs varied across hospitals. CONCLUSION: Most patients received CSFs for neutropenia without fever. Standardized and evidence-based use of CSFs is critically required among hospitals in Japan.