In order to establish a quantitative assay for 8-OHdG concentrations in urine, we examined the precision of a test for the recovery of 8-OHdG in urine by using an ELISA method. The coefficient of variation (CV) for assay with incubation in water or air ranged between 7.0% and 8.4% and between 19.2% and 30.6%, respectively. The data by using incubation in water gave higher accuracy than those in air. The recovery rates of 8-OHdG in urine sample ranged from 95 - 114%. Our results indicated that the excellent sensitivity of this ELISA kit by using incubation in water makes its use possible for the determination in urine with a good reproducibility and recovery of 8-OHdG-spiked samples.