Self-stimulation of the genitals is common in both sexes in pre-school children. For parents who wish to limit this, it usually responds to common-sense techniques such as ignoring or distraction. Persistent or compulsive masturbation may be due to developmental delay or an overall lack of affection. In the absence of such a simple explanation, further investigation is advisable. Masturbation is virtually universal among adolescent boys, but probably occurs in a smaller percentage of girls. Some learning-disabled or autistic young people lack a sense of public propriety, and need to be taught where they can and cannot masturbate. The Children Act rules of consent apply, and the victim may be of sufficient age and understanding to veto the involvement of other agencies. Sexualised play between pre-adolescent children may be normal, although it suggests a worrying lack of supervision. Sexualised activity between adolescents should be regarded as a form of abuse if one party has experienced it as coercive.