Sustained shared thinking (SST) has been identified in the Teachers Standards (Early Years) (2013) as contributing to good progress and outcomes by children. In this paper, I define SST and discuss the outcomes of a study of practitioners' understandings of SST, its challenges and benefits. Writing frames, questionnaires and focus group interviews were used with 19 practitioners. SST was considered a child-initiated interaction with links to co-construction. The interaction occasioned deep-level learning in children, who were often totally absorbed and showed learning which was "sustained" over time. Implications are highlighted, especially the need for additional training in using SST.