Vinorelbine is administered to treat solid tumors such as non-small cell lung cancer and breast cancer, and good treatment results have been reported. Although this agent is known to cause phlebitis, some studies indicated that its administration over 5 minutes or less decreased the incidence of this adverse effect to approximately 5%. However,most studies employed bolus injection, and no study has reported completing drip infusion within 5 minutes. In the present study,we investigated the preventive effects on phlebitis of administering this agent over 5 minutes or less by drip infusion,which is simpler and more useful than intravenous injection. We administered vinorelbine 35 times to 6 patients with breast cancer or non-small cell lung cancer. The mean administration period was 3 minutes and 59 seconds +/-22 seconds, and the incidence of phlebitis was 5.7%. Our administration method involving drip infusion prevented phlebitis as markedly as by intravenous injection. In addition,there were no marked differences in the incidences of adverse effects other than phlebitis. The administration method employed in this study (drip infusion within five minutes) prevented vinorelbine-induced phlebitis, and was simpler than intravenous injection.