Factors influencing nurses'' decisions to raise concerns about care quality.AIM:  To explore factors that influence nurses'' decisions to raise concerns about standards of practice. BACKGROUND:  Health care practitioners have a key role in monitoring care quality. Nurses are required by their professional body to raise concerns about standards; however, under-reporting is the norm. METHOD:  Grounded theory was used to collect and analyse data from semi-structured interviews with 142 practising nurses, theoretically sampled from three Acute NHS Trusts in England. FINDINGS:  Fear of repercussions, retribution, labelling and blame for raising concerns, about which they predicted nothing would be done, were identified as disincentives to raising concerns. Reporting was perceived as a high-risk:low-benefit action. Nurses lacked confidence in reporting systems. CONCLUSIONS:  Disincentives to reporting need to be addressed if an open culture, which promotes quality, safety and learning, is to be developed. Findings give cause for concern and indicate a need to review organizational and professional guidelines, and organizational reporting systems.