In this research, the barriers and enablers to new and different ways of working and role extension in dysphagia care were explored using the grounded theory approach described by Corbin and Strauss (2008). Despite calls for new and innovative ways of providing clinical care, including role extension, researchers have pointed to slow progress amongst Allied Health Professionals (AHPs). Barriers to change that have been identified include professional resistance. Role extension in the field of dysphagia care has made very little progress. The purpose of the research was to construct a substantive theory to help explain the process of role extension in the field of dysphagia care and associated nutrition and detail the enabling conditions and the barriers to these new and different ways of working. In order to explore the process of role extension, data were collected in two phases using semi-structured interviews. The first phase identified the initial theoretical categories and theoretical model; the second phase further developed these categories and refined the theoretical model. Data were collected from two main research settings, with additional data collected from the respective professional bodies and other areas that had initiated role extension. The two main research settings were: an acute and a community care site with limited role expansion in dysphagia, and a combined community and acute Trust with a nationally celebrated programme of role expansion for nurses. Participants included dietitians (n=10), SLTs (n=15), assistant staff (n=2), nurses and other health care professionals (n=8), service users and their carers (6 interviews, n=12), commissioners (n=3) and service managers (n=6). The model and theory developed from the analysis was a shift in the perception and definition of explicit and tacit skills and knowledge. The model that was constructed describes how the professional groups in the domain manipulated this line in order to retain or relinquish professional control over the area. The substantive theory and model developed from this research provides an insight into both how and why professionals at the frontline of dysphagia care in the research settings studied use the tacitness or explicitness of clinical knowledge and skills to retain, or relinquish, control over the clinical area, thus allowing or preventing role extension. Future research may identify that the concepts identified in this research also have applicability in other clinical settings and between other clinical groups