History and Objectives: Due to prevalence of carrier and Streptococcus Pneumonia, its side effects on human population and lack of accurate data on the epidemiology of the disease, the present study was carried out on students of Kashan schools in 1995.

Materials and Methods: A descriptive investigation with random sampling of students in several steps was carried out. Schools were divided into four regions and samples were taken from each region. From each school, 707 individuals were selected systematically. A questionnaire relating to sex, age, school grade, past upper respiratory infection of students and their family, occupation of father and his education level was filled. Throat swab were taken and inoculated on general and selective media and transferred to microbiology laboratory of medical school. On the basis of prevalence of the infection, confidence interval of population was estimated and personal characterization of subjects with infections was determined.

Results: From samples taken, 92 subjects (13%), 20% females and 6.9% males were infected with bacteria. The prevalence among primary school, intermediate and high school students were 17.6%, 8.1% and 7.8% respectively. The spread of the infection was variable in different regions. Selective media separated 16% (With 80% sensitivity and 53% specificity) of bacteria where as only 8% were detected from general media. A correlation between school grade, sex and regions and infection existed (X²=9.44, P=0.002, X²=26.69, P<0.001 and X²=22.43, P<0.001 respectively). No correlation was found between the spread of infection in students and the rate infection in the family members and level of education of father.

Conclusion: Since the infection is fairly prevalence among students especially in younger age, it is suggested that on analytical study on the causes of infection may be carried out. In addition, preventive measures to educate and treating the patients suffering from the disease should be conducted.