Background: Adults with congenital deafblindness (CDB) have received little attention from researchers. In this study we examined the nature of interactions between adults with CDB and the staff who mediate their support, and investigated the reliability of an observation coding system, originally designed for observing adults with severe intellectual disability. Method: The behaviours of 9 adults with CDB, including their interactions with support staff from 2 community residences, were recorded and subsequently coded by 2 observers. Results: Interrater reliability, measured using Cohen's k, was variable across the coding system. Adults with CDB were predominantly observed to be disengaged, with few observations of engagement according to the coding schedule's definition of engagement. Interactions between the residents and support staff were rare. Conclusion: The introduction of interventions designed for staff to promote resident engagement in social interaction is recommended. (Contains 7 tables.)