The purpose of the study was to explore the effect of 2 hour infusion of vancomycin(1g) in 200ml of isotonic saline every 12 hour on the frequency of "red man syndrome", phlebitis and length of peripheral catheter placement of infected patients, in order to provide safe infusion method for reducing vancomycin-induced RMS and phlebitis. The subjects of the study consisted of 16 hospitalized patients; 3 oncology and gastro-intestinal patients, 1 neurological patient, 6 thoracic surgical patients and 6 orthopedic patients, who had received vancomycin from July to October in 1999 at S-hospital. The dependent variables were the incidence of RMS, phlebitis and the length of peripheral catheter placement. The incidence of RMS was checked by an inspector at the first night whenever the infusion method of vancomycin was changed. RMS was observed every 15 minutes during an hour for symptoms of RMS such as itching, erythema, chest pain and systolic blood pressure. Incidence of phlebitis was assessed by inspector twice a day from the insertion of peripheral catheter to the removal of the catheter. The data were analyzed by percentage, mean, X2-test, t-test, repeated ANOVA, and logistic regression analysis using the SPSSWIN program. The results are summarized as follows; 1. No significant difference was identified in frequency of RMS between the experimental group and control group. 2. There was no significant difference in the change of systolic blood pressure as the time goes on between the experimental group and control group. 3. The incidence of phlebitis was significantly lower in the experimental group than in the control group. 4. The length of peripheral catheter placement was significantly longer in the experimental group than in the control group. 5. Other drugs administrated with vancomycin didn't influence the occurrence of phlebitis. However, the infusion method of vancomycin influenced the occurrence of phlebitis. The results suggest that 2 hour infusion of vancomycin(1g) in 200ml of isotonic saline every 12 hours may decrease the incidence of phlebitis and increase the length of peripheral catheter placement compared to 1 hour infusion of vancomycin(1g) in 100ml of isotonic saline every 12 hours. However, it does not reduce the incidence of RMS.