Introduction & Objective: The role and frequency of HHV-6 and HHV-7 in central nervous system (CNS) diseases of our children are unclear. The aim of this study was to search for the presence of HHV-6 & HHV-7 DNA-s in CSF samples in children with meningoencephalitis. Materials & Methods: In a cross- sectional study (2007-2009) done in the pediatric ward in Hazrat Rasoul hospital, Tehran ,Iran ,150 CSF samples were obtained from children with meningoencephalitis. The conventional and BACTEC Ped Plus medium Latex agglutination tests and in some cases bacterial PCR assay were used. We examined the DNA-s of HHV-6 & HHV-6 quantitavively by real time - PCR in the CSF samples.

Results: Cases were 91 (60.7%) male 59 (39.3%) female 1-180 months old. Fever (>38.5° C) was observed in 74% irritability in 70% and convulsion in 53% of cases. All herpes viruses were detected in 18 (12%) cases, HHV-6 DNA was detected in 6 cases and HHV-7 DNA detected in 2 cases with no correlation with age, sex and clinical signs.

Conclusion: HHV-6 & HHV-7 were found in nearly 6% of all studied cases. HHV-6 was slightly more frequent than HHV-7 and its incidence is lower .Our data indicates that herpes viruses are not uncommon causes in children with meningoencephalitis. Our findings are different from those of previous studies perhaps due to the epidemiologic and geographic variations (differences in methods and age groups should be added to this).