The effects of carnosine and related compounds (CRCs) including anserine, homocarnosine, histidine, and β-alanine on monosaccharide autoxidation and H2O2 formation were investigated. The incubation of CRCs with D-glucose, D-glucosamine, and D, L-glyceraldehyde at 37oC increased the absorption maxima at 285 nm, 273 nm, and 290∼330 nm, respectively. D, L-glyceraldehyde was the most reactive sugar with CRCs. The presence of copper strongly stimulated the reaction of carnosine and anserine with D-glucose or D-glucosamine. Carnosine and anserine stimulated H2O2 formation from D-glucose autoxidation in a dose-dependent manner in the presence of 10 μM Cu (II). The presence of human serum albumin (HSA) decreased their effect on H2O2 formation. Carnosine and anserine has a biphasic effect on α-ketoaldehyde formation from glucose autoxidation. CRCs inhibited glycation of HSA as determined by hydroxymethyl furfural, lysine residue with free ε-amino group, and fructosamine assay. These results suggest that CRCs may be protective against diabetic complications by reacting with sugars and protecting glycation of protein.