This paper reports on a study of the prevalence and social correlates of dyssomnias, features associated with obstructive sleep apnoea, and parasomnias in primary school children aged 4-12. Head teachers of schools selected randomly from lists of local primary and special schools were contacted by telephone and asked to distribute a questionnaire package to the parents of all pupils aged 4-12 years. In all, 890 parents of children from mainstream schools and 300 from special schools were approached. The response rates were 64.7% and 60%, respectively. The results showed that significantly higher proportions of children in special schools than in mainstream schools presented four of the five dyssomnias investigated and all of the features associated with obstructive sleep apnoea. In contrast, only two of the seven parasomnias were presented by higher proportions of the children in special schools. Age and gender differences for the two groups of children are presented. Finally, multiple correlations were computed between a range of child, family, and environmental characteristics and the three problems most frequently reported: frequency of settling problems; sleeping in the parents' bed; and night waking. The findings are discussed with reference to other studies of children's sleep problems, and the implications for treatment are considered.