We tried to reveal the prevalence rates of the head louse infestation in school children in Kangwon-do, Korea in December 1990. A total of 912 children in four primary schools was examined. The positive rate for adults and/or nits of Pediculus humanus capitis was 37.2%. One school was followed-up without specific intervention. There was no significant change of the prevalence rate 6 months after the first examination from 66.0% to 57.3%. We could see the persistent infestation rate if there was no intervention. We are emphasizing the significance of worm positive rate because it represents the potentiality of active transmission.