According to the prescribing information, pegfilgrastim should not be administered within 14 days prior to, or within 24 hours after, the administration of cytotoxic chemotherapy. However, few data exist to support this recommendation. A single-institution retrospective review was conducted of all patients with ovarian or primary peritoneal cancer who received prophylactic pegfilgrastim on the same day as myelosuppressive chemotherapy from May 2003 to June 2006. Forty-six patients were treated for the following malignancies: 35 (76%) epithelial ovarian, 6 (13%) primary peritoneal, and 5 (11.0%) ovarian germ cell or stromal cell carcinoma. All patients met the current guidelines of using colony-stimulating factors for prophylaxis against febrile neutropenia. A total of 269 cycles of chemotherapy were administered. All patients received pegfilgrastim within 1 hour of the completion of chemotherapy administration. Grade 1 or 2 neutropenia developed in 10 cycles (3.7%), and the mean absolute neutrophil count was 4926/uL (range, 1,293-24,300). No patients had febrile neutropenic episodes, hospitalizations, or antibiotic use secondary to neutropenia, nor did they have dose reductions or chemotherapy delays due to neutropenia. Administration of pegfilgrastim on the same day as myelosuppressive chemotherapy in patients with ovarian or primary peritoneal cancer may be determined to be a convenient, safe, and effective approach.