Predictive genetic testing should only be performed on children if it is in their best interests. "Interests" include psychosocial elements. Predictive testing is performed on children when there are interventions to prevent disease or to detect and treat it early and it is necessary to begin these interventions in childhood. It is also performed for diseases known to commence in childhood. Predictive testing in children for adult-onset conditions for which there is no medical intervention is highly controversial. Competent children and adolescents can consent to predictive genetic testing. Predictive testing can result in harm, such as discrimination (eg, in insurance entitlement or employment) and stigmatisation. Predictive testing can have important non-medical benefits in terms of self-knowledge and life planning.