Aims and objectives. The purpose of this study was to explore factors that may affect nurses' use of nursing diagnoses in charting standardized nursing care plans in their daily practice. Background. Care plans have been viewed as providing a structured approach to the assessment, planning and delivery of patient care. Nonetheless, the challenge for many institutions is to help professional nursing staff refine their understanding of nursing diagnoses and charting skills, to identify patient problems and propose appropriate care plans. Method. Twelve clinical nurses working at a medical center in Taiwan underwent one-on-one in-depth interviews from May to July 2000. Data analysis was based on Miles and Huberman's data reduction, data display, and a conclusion verification process to investigate the charting process. Findings. Nurses tended to match patient conditions to the designated nursing diagnoses, be unfamiliar with statements of related factors, use objective data to describe patient conditions, ignore descriptions of nursing goals, dutifully check interventions without always executing them, and choose the same evaluation to meet hospital requirements. Conclusions. These findings suggest that using educational programmes for enhancing nurses' ability to use nursing diagnoses and exploring the process of diagnostic reasoning would improve the quality of patient documentation. Relevance to clinical practice. The trend in health care is to focus on chart audit to reveal indicators of quality of care. Therefore, the experience of nurses in this study could be applied to in-service training programmes by institutions that are replacing traditional, manually written care plans with a standardized care planning system, thus helping other nurses through this transition process.