Viral meningitis and encephalitis are important and serious diseases in young children and adults. There are many causative viruses but it is known that a low percentage of adenovirus (ADV) and parvovirus (PAV) infected individuals develop meningitis or encephalitis. Few reports have been published about central nervous system complications that were rare but fatal. First we used enzyme immunoassay (EIA) with monoclonal antibody to detect ADV antigen (Ag) and PAV Ag in cerebrospinal fluids (CSF) from acute phase of hospitalized adult patients with viral meningitis or viral encephalitis. Second we detected ADV DNA and PAV DNA in the same CSF after cell culture by nested-polymerase chain reaction (PCR). Third we evaluated ADV and PAV dual infection in CSF by EIA and nested-PCR. ADV Ag in CSF by EIA positivity was 42.9% (12/28) and PAV Ag in CSF by EIA positivity was 21.4% (6/28). ADV DNA in CSF by nested-PCR positivity was 89.3% (25/28) and PAV DNA in CSF by nested-PCR positivity was 38.5% (10/26). ADV and PAV dual infection in CSF by nested-PCR was 35.7% (10/28). Detection rate of ADV DNA and PAV DNA in CSF by nested-PCR with viral meningitis or encephalitis adult patients were higher than we expected. Positive detection of nested-PCR was higher than that of EIA with monoclonal antibody for detection of antigens ADV and PAV in CSF with viral meningitis or encephalitis adult patients. Both methods were analnized by the McNemar test.