This study on children with a Pervasive Developmental Disorder (PDD; N = 32), children with developmental language disorder (N = 22), and normally developing children (N = 28) sought to answer questions concerning attachment and autistic behaviour. We could replicate the finding that children with a PDD are able to develop secure attachment relationships to their primary caregiver. Children with PDD who had an insecure attachment showed fewer social initiatives and responses than children with PDD who had a secure attachment, even when the insecurely and securely attached PDD children were matched on chronological and mental age. Children with both a PDD and mental retardation were more often classified as disorganised. Three findings suggested that a disorganised attachment does not merely reflect the presence of "autistic" behaviour: (1) children with PDD did not reveal higher rates of a disorganised attachment than matched comparison children; (2) having a PDD diagnosis and having a disorganised attachment were found to be associated with opposite effects on an ethological measure of level of behavioural organisation; and (3) a disorganised attachment but not a PDD diagnosis was associated with an increase in heart rate during parting with the caregiver and a decrease in heart rate during reunion.