Herpes simplex virus type 1 establishes a latent infection in the peripheral nervous system following primary infection. During latent infection, virus genome exhibit limited transcription, with the HSV LATs consistently detected in latency infected ganaglia. Following ocular infection viral latency develops in the trigeminal ganglia. In this study PCR has been used for detection of HSV-1 nucliec acid . BALB/c mice were inoculated with HSV-1 and infected mice ganglia were applied to detect HSV-1 TK gene. Amplification of TK fragment in mice ganglia was considered as an indicator of viral latency. The results were suggested that TK PCR can be used as a reliable diagnostic tool and it is a specific and highly sensitive method for the detection of HSV genome in trigeminal ganglia.