Emotional and behavioural disturbance was assessed in 82 individuals with severe intellectual disabilities and challenging behaviour using the Diagnostic Assessment for the Severely Handicapped-II (DASH-II). Levels of disturbance were compared firstly in individuals with and without features of autism as assessed by the DASH-II, and secondly in individuals with varying severities of autism. In both cases levels of ability and overall severity of behaviour disorder were comparable across groups. Individuals with autistic features were found to have significantly higher scores than nonautistic individuals on the DASH-II organic disorder, anxiety, mania, PDD/autism and stereo types subscales. When participants with autistic features were separated into groups of severe and moderate autism and compared with nonautistic participants, significant effects of group were found for scores on the anxiety, mood, mania, PDD/autism, schizophrenia and stereotypies subscales. Scheffe tests were conducted to further evaluate between-group differences. Item analysis showed seven DASH-II items to have a 30% or more difference between levels of endorsement in autistic and nonautistic individuals, with six further items showing a 20% or greater difference in levels of endorsement. Findings are compared to those from previous research and implications for the conceptualisation of emotional and behavioural disorders in individuals with autism are discussed.