Pediculosis capitis (head lice infestation) is a worldwide public health concern affecting mostly primary-school children. In a cross-sectional study in 2009/2010, the prevalence of pediculosis capitis and some risk factors for infestation were investigated among 1550 randomly selected primary-school children in Mafraq governorate, Jordan. The prevalence of pediculosis capitis was 26.6%. There were significant differences in the prevalence between girls (34.7%) and boys (19.6%), rural (31.2%) and urban (23.5%) residents, and history of infestation in the previous year (57.4%) versus no history (11.5%), as well as between children of different ages, family size and income (P<0.001). Longer hair length, lack of bathing facilities, low frequency of hair-washing and bathing, and sharing of articles (e.g. combs, scarves) were significantly associated with infestation (P<0.001). The prevalence of infestation was higher than reported in previous studies in Jordan (< 14%). Programmes are needed to increase awareness of pediculosis capitis and the importance of good personal hygiene.