Finding lice can be difficult in head louse infestation. We compared a new louse detection comb with visual inspection. All children in two rural Turkish schools were screened by the two methods. Those with lice were offered treatment and the results monitored by detection combing. Children with nits only were re-screened to identify latent infestations. Using visual inspection we found 214/461 children (46%) with nits but only 30 (6·5%) with live lice. In contrast detection combing found 96 (21%) with live lice, of whom 20 had no nits. Detection combing was 3·84 times more effective than visual inspection for finding live lice. Only 10/138 (7·2%) children with nits and no lice were found to have active infestation by day 16. We found that the detection comb is significantly (P<0·001) more effective than visual screening for diagnosis; that nits are not a good indicator of active infestation; and that treatment with 1% permethrin was 89·6% effective.