Aminoguanidine (AG) is a prototype therapeutic agent for the prevention of formation of advanced glycation endproducts. It reacts rapidly with alpha,beta-dicarbonyl compounds such as methylglyoxal, glyoxal, and 3-deoxyglucosone to prevent the formation of advanced glycation endproducts (AGEs). The adducts formed are substituted 3-amino-1,2,4-triazine derivatives. Inhibition of disease mechanisms, particularly vascular complications in experimental diabetes, by AG has provided evidence that accumulation of AGEs is a risk factor for disease progression. AG has other pharmacological activities, inhibition of nitric oxide synthase and semicarbazide-sensitive amine oxidase (SSAO), at pharmacological concentrations achieved in vivo for which controls are required in anti-glycation studies. AG is a highly reactive nucleophilic reagent that reacts with many biological molecules (pyridoxal phosphate, pyruvate, glucose, malondialdehyde, and others). Use of high concentrations of AG in vitro brings these reactions and related effects into play. It is unadvisable to use concentrations of AG in excess of 500 microM if selective prevention of AGE formation is desired. The peak plasma concentration of AG in clinical therapy was ca. 50 microM. Clinical trial of AG to prevent progression of diabetic nephropathy was terminated early due to safety concerns and apparent lack of efficacy. Pharmacological scavenging of alpha-oxoaldehydes or stimulation of host alpha-oxoaldehyde detoxification remains a worthy therapeutic strategy to prevent diabetic complications and other AGE-related disorders.