In this study, cysteine compounds found in genus Allium plants, including N-acetyl cysteine(NAC), S-allyl cysteine(SAC), S-ethyl cysteine(SEC), and S-methyl cysteine(SMC), were examined for effects on blood glucose, glucose tolerance, and plasma lipid concentrations in streptozotocin(STZ)-induced diabetic mice. In the mice, the ingestion of these cysteine compounds did not affect blood glucose levels significantly. However, their ingestion did improve the diabetic symptoms of polydipsia, polyphagia, polyuria, and weight loss. Glucose tolerance was also found to be improved in the STZ diabetic animals by feeding the cysteine compounds. Treatment of the compounds also caused a slight decrease in plasma concentrations of total cholesterol along with increases in HDL-cholesterol and slight decreases in LDL-cholesterol, resulting in a significant decrease in the atherogenic index of plasma in the diabetic animals. They also showed reductions of liver triglyceride content to relieve diabetic fatty liver syndrome. In summary, the cysteine compounds such as NAC, SAC, SEC, and SMC, found in genus Allium plants, had certain beneficial effects on blood glucose metabolism along with preventing abnormalities in lipid metabolism, a complication of diabetes, by improving the atherogenic index of plasma and fatty liver in STZ-induced diabetic mice.