An electrochemical DNA-biosensor has been used to investigate the interactions between DNA and members of a group of ten derivatives of 1,3,5-triazine herbicides: chloro-s-triazines (atrazine, propazine, terbutylazin, and cyanazin), thiomethyl-s-triazines (ametryn, prometryn, terbutryn, and simetryn), and methoxy-s-triazines (prometon and terbumeton). A UV spectrophotometric study of this group of herbicides was also undertaken. Of this group only cyanazin could be oxidized in aqueous solution using a glassy carbon electrode. Use of the electrochemical DNA-biosensor revealed the occurrence of a time-dependent interaction of all the herbicides with DNA, via the appearance of guanine, guanosine, and adenosine oxidation signals that correspond to DNA damage. Adduct formation between the herbicide and the DNA purine bases guanine and adenine is suggested as a mechanism.