The aim of the present study was to investigate the effects of biologically important catechols on the cytotoxicity of adriamycin, farmorubicin, and mitomycin C with respect to hydroxyl radical production. Catecholamines (adrenalin, noradrenaline, dopamine) and DOPA enhance the generation of hydroxyl radicals by chemotherapeutic antibiotics. Measures were done using a deoxyribose assay, in presence of the Co(II) + H2O2 system. Catalase and hydroxyl radical scavengers (mannitol, thiourea, cysteine, glutathione, L-lactic dehydrogenase) inhibited the deoxyribose damage caused by the drugs.