RESUMO
The study of premarital sexual intercourse in 350 Thai students aged 18-20 years in commercial schools showed that 151 subjects (43.1%) having premarital sexual intercourse--50.3 per cent never used condoms, 25.8 per cent used sometimes and 23.8 per cent used everytime. Their sexual partners were girl friends in 78.1 per cent and sex workers in 18.5 per cent. The average age of first sexual intercourse was 16.6 years. There were 87 subjects who had symptoms similar to sexually transmitted diseases. Single void-urine was tested for past and present C. trachomatis infection. There were 8 of 350 subjects (2.3%) with positive results for the leukocyte esterase activity in urine samples but only 2 cases (0.6%) were positive for C. trachomatis antigen and antibody. Detection of C. trachomatis DNA was negative in all urine samples. The antibody detection in urine samples was 11.1 per cent and in blood samples 22 per cent. There was no correlation with r = 0.3 of optical density values between urine and blood samples.