Pediculosis, the infestation with Pediculus humanus, is found wherever personal or general hygiene is at a low level. A prevalence survey of Pediculus humanus among elementary school students aged 6-10 years in Bang Phli District, Samut Prakan province, Thailand was undertaken from January 2000 to March 2000 to determine pediculosis status and related factors. There were 764 subjects, 360 male and 404 female. It was revealed that 1) Pediculus humanus were found in 26.00% of the students, 3.10% in male and 46.50% in female, 2) there was a correlation between prevalence of pediculosis and student sex and the family socio-economic income (p < 0.01, X²), and 3) student ages had no relationship with the prevalence of pediculosis. (p > 0.05, X²)