The type, frequency and inter-relationships of emotional and behavioural problems in 863 children with autism spectrum disorder (ASD) were investigated using the population-based Database of children with ASD living in the North East of England (Dasl(n)e). A high rate of problems was reported, with 53 % of children having 4 or more types of problems frequently. Sleep, toileting and eating problems, hyperactivity, self injury and sensory difficulties were greater in children with lower language level and in special schooling. However, anxiety, tantrums and aggression towards others were frequent regardless of age, ability or schooling. The frequency of co-existing conditions, including such emotional and behavioural problems, in children with ASD has implications for designing appropriate support services for children and families.