Streptococcus pneumoniae is the worldwide leading causative agent of community acquired pneumonia and meningitis with high morbidity and mortality. Pneumonia and meningitis are the two most frequent manifestations of S. pneumoniae. However, only. a small proportion of the cases can be detected by conventional methods such as blood culture. The recently developed pneumolysin PCR method can detect low numbers of organisms or even DNA fragments even without live cells of the pathogen. Penumolysin is a species specific 52 kDa protein found in all strains of S. pneumoniae and is an ideal target for antigen detection. We detected S. pneumoniae in sera (n=29) from hospitalized children with respiratory infection, and cerebrospinal fluids (n=57) from hospitalized adults and children with viral meningitis. ELISA using anti-So pneumoniae monoclonal antibody and PCR detection of the pneumolysin gene were applied to the clinical specimens from October 1998 to July 2001. In the children with respiratory infection, PCR detection of the peripheral blood monocytes showed 37.9% (11/29) of positivity, while ELISA using sera gave only 18.5% (5/27) of positivity. In the adult patients with viral meningitis, PCR detection of cerebrospinal fluids showed 41.4% (12/29) of positivity, and ELISA gave 35.3% (6/17) of positivity. With cerebrospinal fluids of children with viral menigitis, PCR showed 42.3% (11/26) of postivity, while ELISA gave 26.9% (7/26) of positivity. PCR detection of S. pneumoniae pneumolysin gene applied to peripheral blood monocytes and heated cerebrospinal fluid samples appeared to be a more specific diagnostic test than the conventional cultural methods in S. pneumoniae infections.