The polymerase chain reaction (PCR) enables rapid and sensitive detection of VZV and HSV DNA and its efficiency depends mainly on the choice of the primers. Primers should hybridize to conserved DNA sequences within the viral genomes i n order to avoid unreliable amplification due to DNA sequence variation between different strains. The aim of the study was t o design and to evaluate a general primer pair which permits fast and reliable detection of HSV and VZV. The genes UL 15 of HSV and UL 42 of VZV share the highest degree of homology within the two genomes. We designed a primer pair (GPHV-RU) which hybridizes t o these genes. The genetic variability of amplified sequences from clinical specimens was analyzed by restriction enzyme cleavage analysis and by temperature gradient SSCP analysis (TG-SSCP). PCR with GPHV-RU amplified viral sequences from all analyzed specimens (25xVZV, 1OxHSV-1, 5xHSV-2) obtained from patients with clinical evidence of HSV or VZV infection. Restriction enzyme cleavage analysis with Hpa II further permitted reliable distinction between VZV, HSV-1, and HSV-2. Analysis of the heterogeneity of the amplified sequences by restriction enzyme cleavage and by TG-SSCP demonstrated no variability between the analyzed clinical specimens of VZV and of HSV-2 and only one differing TG-SSCP-pattern within the HSV-1 isolates. The results suggest that detection of HSV and VZV using the new primer pair GPHV-RU should give reliable results as the amplified sequences show little genetic variability within clinical isolates of HSV-1/2 and VZV.