A novel histochemical method was compared with a cytopathic effect (CPE) assay for the identification of herpes simplex virus (HSV) in clinical specimens. The method utilizes a stably transformed cell line (BHKICP6LacZ- 5) that expresses β-galactosidase only after infection with HSV. A total of 96 specimens submitted to our diagnostic virology laboratory were analyzed. Thirty-one specimens contained HSV as evidenced by positive CPE, and all were positive for β-galactosidase staining. CPE were not evident for 2 or more days in 15 of the 31 positive specimens, whereas the histochemical stain was positive in all 31 positives by 16 to 24 h. This preliminary study shows that the BHKICP6LacZ-5 cell line can be used in a rapid, sensitive, and specific assay for the detection of HSV in clinical specimens.