The potential use of oxidative stress-induced DNA and RNA damage products as biomarkers is an important aspect of biomedical research. There is a need for assays with high specificity and sensitivity that also can be used in molecular epidemiology studies with a large number of subjects. In addition there is a need for assays that can measure more than one product from DNA oxidation. We present a sensitive, precise, and accurate method for quantitative analysis of the oxidized nucleosides 8-oxoGuo and 8-oxodG in human urine. The assay is based on automated sample handling using a BIOMEK 3000 Workstation, and UPLC-ESI(+)-MS/MS analysis. High specificity is evidenced by the use of qualifier ions for both analytes. The quantification limit in urine samples is 1 nM for both analytes. Accuracy and precision were documented, showing average recoveries of 106.2% (8-oxoGuo) and 106.9% (8-oxodG), and overall precision (within-day and between-days) of 6.1 and 4.4%, respectively.