The Mental Capacity Act 2005 (MCA) introduced safeguards to protect people who lack capacity from intrusive research. Whilst these safeguards stemmed from predominantly medical ethical review concerns and developments aimed at protecting people from physical and psychological damage and harm, the Act relates to all forms of research. The implications of the requirements of the Act for the conduct of social care research and the identification of helpful approaches or development of new knowledge concerning people who may lack capacity are as yet unknown. There are some concerns that the Act does not fully account for social research, recognise its importance to and differences from health-related research and may even hamper such research from taking place. This paper describes the findings and implications from a Social Care Institute for Excellence (SCIE)/Department of Health (DH) funded research project that considered the impact of the Mental Capacity Act 2005 on the ethical scrutiny and development of social care research. The particular focus of the study was processes relating to university research ethics committees (URECs). The study was undertaken in two stages beginning with an on-line survey of UREC policies and procedures and followed by interviews with social care researchers working in areas in which people may lack capacity according to the terms of the Act. Recommendations for research ethics review are made that will be of importance to practitioners, policy-makers and researchers.