The aim of this study was to evaluate agreement between nurses' and physicians' opinions regarding aggressiveness of treatment and to investigate and compare the rationales on which their opinions were based. Structured interviews regarding 714 patients were performed on seven general wards of a university hospital. The data gathered were then subjected to qualitative and quantitative analyses. There was 86% agreement between nurses' and physicians' opinions regarding full or limited treatment when the answers given as 'uncertain' were excluded. Agreement was less (77%) for patients with a life expectancy of less than one year. Disagreements were not associated with professional status because the physicians considered limiting life-sustaining treatment as often as the nurses. A broad spectrum of rationales was given but the results focus mostly on those for full treatment. The nurses and the physicians had similar bases for their opinions. For the majority of the patients, medical rationales were used, but age and quality of life were also expressed as important determinants. When considering full treatment, nurses used quality-of-life rationales for significantly more patients than the physicians. Respect for patients' wishes had a minor influence.