This study investigated whether the Communication Checklist-Adult (CC-A) could identify subtypes of social and communication dysfunction in autism probands and their parents. The CC-A is divided into subscales measuring linguistic ability as well as two aspects of social communication: the Pragmatic Skills subscale assesses the level of pragmatic oddities (e.g. excessive talking), while the Social Engagement subscale picks up on those behaviours that reflect a more passive communication style (e.g. failure to engage in social interactions). CC-A data were collected for 69 autism probands, 238 parents of autism probands and 187 typical participants. The CC-A proved sensitive to the communication difficulties of autism probands and a proportion of their parents. The majority of parents who demonstrated the broader phenotype scored poorly on either the Pragmatic Skills or Social Engagement scale only. The Social Engagement scale was particularly sensitive to the difficulties of the parents, indicating that social-communicative passivity may be an important part of the broader autism phenotype. The findings provide evidence for the existence of more constrained pragmatic phenotypes in autism. Molecular genetic studies in this area may benefit from stratifying samples according to these phenotypes. (Contains 5 tables and 1 figure.)