To determine the prevalence of and assess risk factors associated with head lice infections (pediculosis) in children from government primary schools in Victoria, Australia. Between May and October 2001, children were selected by clustered random sampling of schools and classes, then examined for head lice using hair conditioner and a fine-toothed head lice comb. There were 1838 children screened from 16 primary schools. Risk factors evaluated included metropolitan or rural residence, school class, gender and hair length. Thirteen percent of children (239/1838) had an active infection (95% CI, 10.9-15.1) and 3.3% (61/1838) had an inactive infection (95% CI, 2.0-4.6). Prevalence of active pediculosis varied between schools from 0 to 28%. Our screening identified no more than one case per class in the majority of classes screened (58.5%). Females were 2.2 times more likely to have active infection than males (95% CI [1.7,2.9]) and there was no significant difference for the other risk factors investigated. Our study demonstrated the prevalence of head lice varied across Victoria and showed that risk factors commonly attributed to head lice infections did not hold true. Our findings support the premise that traditional ad hoc mass school-based screening may not be the best use of resources when controlling head lice. We suggest a more pragmatic community-based approach.