HSZP strain of herpes simplex virus type 1 (HSV-1) - unlike strains KOS, SC16 and ANGpath - established latency in the homolateral trigeminal ganglion of mice at a limited rate (21%) when tested by reactivation of latent virus in culture. If a nested polymerase chain reaction (PCR) for virus DNA detection was used, the positivity rate was 63 - 100%. The detection rate of HSZP DNA in acutely infected gangla did not differ from that of SC16 DNA provided that the sensitivity of PCR was below 20 pg of HSZP DNA per 0.5 mu g of total ganglionic DNA. The nested PCR assessed at least 200 fg of HSZP DNA per 0.5 mu g of ganglionic DNA.