OBJECTIVE Evidence-based clinical practices can improve patient outcomes, especially in the area of chemotherapy. In Japan, it is not known how well physicians adhere to evidence-based chemotherapy guidelines. This study aimed to assess physician compliance with national guidelines for ovarian cancer primary chemotherapy in Japan. METHODS Using an administrative database, we analyzed 209 cases of surgical laparotomy without neoadjuvant chemotherapy as the primary intervention for adnexal cancer. Cases were identified across seven teaching hospitals between 2003 and 2006. RESULTS Of the 136 patients receiving inpatient chemotherapy, 101 cases (74%) were treated with platinum-taxane therapy. In five hospitals, platinum-taxane therapy was used in more than 75% of patients, compared to 56% and 32% in the other two hospitals, respectively. The proportion of patients receiving paclitaxel and carboplatin concomitant therapy (TC therapy) was 67%, although significant variation was noted between hospitals (range 32% to 94%, P < 0.001). Of the 91 patients receiving TC therapy, 59 (65%) were given full-dose monthly regimens, while 32 cases (35%) were treated with divided doses weekly. Weekly TC therapy was more frequently provided in hospitals with a low volume of patients receiving TC therapy. Patients under the age of 65 receiving inpatient chemotherapy were more likely to receive full-dose regimens than patients 65 or older (68% vs 43%, P = 0.005). Publication of national treatment guidelines did not appear to substantially impact chemotherapy practice patterns. CONCLUSIONS Adherence to standardized chemotherapy was comparable to rates in European countries, although rates among hospitals differed significantly. Elderly patients were more likely to receive divided-dose regimens.