For years, trachoma screening has been a routine part of the health examination program for all primary school children. In order to ascertain the current prevalence of trachoma in primary school children, we used clinical examination, immunofluorescein-monoclonal antibody and McCoy cell culture technique to examine 771 children from 5 primary schools in Kaohsiung City. Using the results of the McCoy cell culture as a judgement standard, we found that 118 children (15.3%) had chlamydia trachomatis infections. The infection rates of children were statistically insignificant for sex, grade and location of school of children. Among the 118 infected children, most had none or mild (96.6%) conjunctival inflammation. Only 3 children (0.4%) had conjunctival cicatrization complications. These results showed that the repeated reinfections among these children were quite few. The McCoy cell culture was used to test the result of clinical diagnosis made by the senior ophthalmologists. The sensitivity of the clinical diagnosis was 50% and the predictive positive rate was 26.6%. It revealed that the diagnosis of trachoma made by clinical observation only was unreliable. The results of immunofluorescein-monoclonal antibody test showed that 120 children (15.6%) had trachomatous infections. Its sensitivity was 68.4%, and specificity was 91.7%. It revealed that more care should be taken in quality control of laboratory techniques. From these results, we conclude: 1) the trachomatous infections of primary school children in Kaohsiung City are not serious; the repeated infections among