Chlamydia Pneumoniae (C. pneumoniae) is a bacterium involved in infections of the upper airway as well as in lower respiratory diseases. It has been reported that infections from this bacterium are prevalent worldwide and that the proportion of the population having the antibody is high. It is, however, difficult to identify the pathogen by routine bacterial examination because it is an obligate cytozoic bacterium. In addition, the examination has been feasible in only a limited number of laboratories because the determination of the serum antibody titer has required preparation of the antigen as well as sophisticated skill. We conducted an epidemiological survey of 320 healthy males and females in their 20s living in the three cities of Osaka, Kobe and Oita using "HITAZYME C. Pneumoniae", which is a recently developed kit for determination of anti-C. pneumoniae specific antibody. The statistical method used was the chi square test for the comparison of proportions. Mean proportion of the population showing positive antibody test was 58.1%. IgA antibody was positive in 42.8% and IgG in 46.5% of the above population. There were no statistically significant differences between districts of between genders in the percentages of cases positive for these antibodies. The results were comparable to those previously reported suggesting that C. pneumoniae is prevalent all over Japan. This kit was found to be an easy way to use the ELISA method and therefore to be clinically useful.