At our hospital, we use aprepitant for nausea and vomiting when administering highly emetic anticancer agents, according to "Guidelines for the Appropriate Use of Antiemetic Agents" given by the Japan Society of Clinical Oncology. We initiated the intravenous administration of fosaprepitant for better compliance compared with aprepitant; however, we observed phlebitis after the infusion of fosaprepitant. Therefore, we investigated measures to reduce phlebitis associated with the infusion of fosaprepitant. For the first premedication, fosaprepitant (150 mg) was dissolved in 100 mL of saline and administered for 30 minutes; 1 of 2 patients showed grade 4 phlebitis. For the modified premedication, fosaprepitant, dexamethasone, and 5- HT(3) antagonist were dissolved in 100 mL of saline and administered for 30 minutes. The modified premedication was administered to a total of 27 patients; 5 patients developed mild phlebitis (grade 1), but infusion could be continued by treating their phlebitis with a hot pack. We used a combination of dexamethasone and 5-HT(3) antagonist with fosaprepitant as a modified premedication in order to avoid drug-induced vascular damage, which resulted in the pH decreasing to 6.20-7.55 (close to neutral) and a shorter infusion time.