DNA polymerases involved in ultraviolet (UV)-induced DNA repair were studied in human fibroblasts using the inhibitors of DNA polymerases, aphidicolin which inhibits DNA polymerases alpha, delta and epsilon, and butylphenyldeoxyguanosine (BuPGdR) which inhibits DNA polymerase alpha strongly and weakly inhibits delta and epsilon. Both inhibitors inhibited replicative DNA synthesis in a dose dependent manner as measured by thymidine incorporation. However, BuPGdR did not accumulate single strand breaks in cells irradiated with 5 J/m2 UV-light even at the highest dosage tested, indicating that BuPGdR does not inhibit DNA repair. On the other hand, aphidicolin accumulated single strand breaks in UV-light irradiated cells. These results suggest that DNA polymerase delta and/or epsilon are mainly involved in UV-induced DNA repair.