Background: This study examined risk factors for the development of psychopathology in children with intellectual disability (ID) in the developmental, biological, family and social-ecological domains. Methods: A population sample of 968 children, aged 6-18, enrolled in special schools in the Netherlands for educable and trainable ID were assessed at Time 1. A random 58% were re-contacted about 1 year later, resulting in a sample of 474 at Time 2. Results: Psychopathology was highly consistent over 1 year. Risk factors jointly accounted for significant, but small, portions of the variance in development of psychopathology. Child physical symptoms, family dysfunction and previous parental mental health treatment reported at Time 1 were uniquely associated with new psychopathology at Time 2. Conclusions: Prevention and early intervention research to find ways to reduce the incidence of psychopathology, possibly targeting family functioning, appear important. © 2006 Blackwell Publishing Ltd.