A role for oxidative DNA damage has been implicated in many diseases, including the major pathologies such cancer and heart disease. The assessment of damage in biological matrices, such as DNA, serum and urine, is vital to understanding this role and devising intervention strategies. Despite the numerous techniques to measure oxidative DNA damage products in urine, what these measurements truly represent seems unclear. Sources of urinary lesion may include the diet, cell death, and of most interest, DNA repair. Were it possible to exclude the two former contributions, a urinary assay for DNA repair would be invaluable in the study of DNA damage and disease. Significant work still needs to be performed to examine these three parameters and hence further elucidate the kinetics of lesion formation and clearance in vivo. Upon establishment of these details, urinary oxidative DNA damage measurements may become more than a reflection of generalised oxidative stress. Studies from our laboratory, and others, are making appreciable progress towards the interpretation of urinary lesion measurements and the development of urinary repair assays.