General practice-based research activity is increasing rapidly, particularly for large, collaborative, multi-centre studies. We conducted semi-structured interviews with general practitioners and other professionals at practices in the East London and the City Health Authority area, to investigate the difficulties presented by becoming involved in these studies. Interviewees' main concerns were: time constraints; team motivation; the perception that external researchers have unrealistic expectations; the need for good communications throughout and, specifically, for good feedback from these researchers.