Aminoguanidine (AG), a prototype therapeutic dicarbonyl scavenger, is the most potent drug available today to inhibit the formation of advanced glycation endproducts (AGEs) and to reverse glycation-mediated damage in normal aging. This paper examines the ability of AG to cause damage to supercoiled plasmid DNA in the presence of the transition metal, Fe+3. Damage to DNA was dependent on the concentrations of both the transition metal and AG. We could detect hydroxyl radical as well as hydrogen peroxide during the incubation of AG with Fe+3. Thus this finding further cautions against the indiscriminate use of AG in clinical prophylaxis in diabetes and questions its use as a therapeutic agent.