Growth of HSV-1 in (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) results in incorporation of the analog into HSV-1 DNA. Employing the technique of Weigle-type reactivation (WR), HSV-1 inactivated by uv irradiation but not by growth in BVDU is a substrate for induced cellular repair pathways. Growth of mammalian cells in BVDU does not induce cellular repair pathways detected by WR. HSV-1 temperature sensitive (ts) mutants demonstrate an increased reversion frequency to the nonpermissive phenotype (ts+) following growth in a high concentration of BVDU. A ts mutant did not display an increased reversion frequency following growth in equally inhibitory concentrations of an HSV-1 polymerase inhibitor, aphidicolin. These findings suggest that BVDU incorporated into HSV-1 DNA may not be readily excised and may be a mutagenic lesion in viral DNA, although other explanations are possible.