The effects of capsaicin, a pungent principle of red pepper, on blood glucose concentrations were studied in streptozotocin-induced diabetic rats. Capsaicin was supplemented at the concentrations of 0.014% or 0.028% in the diet and experimental animals fed the diet for 4 or 8 weeks. Dietary capsaicin didn't show any differences in the ingested food amounts and body weights compared to diabetic control or control. At 3 weeks of capsaicin fed, capsaicin groups showed relatively decreased ad libitum blood glucose levels compared to diabetic control. At 4 weeks of capsaicin fed, diabetic rats fed capsaicin diet (0.028%) showed significantly decreased basal and blood glucose levels on 10, 20 minutes after intravenous glucose tolerance test (p<0.05), but they didn't show any significant decrease thereafter when compared to diabetic control. At 8 weeks of capsaicin fed, capsaicin groups showed relatively same results as 4th week-intravenous glucose tolerance test on oral glucose tolerance test. Immunoreactive insulin levels and plasma free fatty acids were not changed between the groups, but plasma free fatty acids are relatively decreased in capsaicin-fed group compared to diabetic control. Dietary capsaicin showed significant influence on glucose transporter 4 mRNA levels tested in gastrocnemius muscle but not in parametrian adipose tissue. Glucose transporter 4 mRNA levels of gastrocnemius muscle increased up to 2.7 times compared to diabetic control by increasing capsaicin intake(p<0.05). This study suggests that capsaicin intake improves the metabolic status like as hypoglycemic effect in diabetic condition, probably because of increased insulin sensitivity.