This study examined the causes of stress experienced by National Health Service nurses in England over the course of a single week with the aim of generating a cognitive structural model. Qualitative data served as the foundation of a network study which employed inductive eliminative analysis. These data were also analysed using conventional qualitative methods and by content analysis. The results were consistent with previous studies that identified a number of primary sources of stress. However, the network study indicated that two systems of causation were operating. The first centres on inadequate staffing levels, which were seen as leading to poor attitudes and abilities among colleagues, multiple work roles and lack of support. Lack of support also contributed to powerlessness and poor attitudes and abilities. The behaviour of managers was strongly endorsed as a direct cause of stress, but the strongest explanatory link was through staffing levels and powerlessness. The second system of causation related patients' suffering to stress. The qualitative data validated the network study results through elaborating the understanding of the respondents' nominated causes. Discussion focused on the pressure and frustration experienced by nurses because of organizational factors and interaction effects with the caring nature of nursing work. It is suggested that nursing discourse is subordinated to managerial and biomedical discourse reflecting the relative powerlessness of nurses. The extent to which such powerlessness is primarily a result of the failure of nurses to assert themselves or intrinsic organizational factors is not clear. The consequences of a stressed and demoralized nursing workforce on the quality of patient care and risk profile are identified as the focus for future research.