Using standardized assessment instruments may help staff identify needs, problems and resources which could be a basis for nursing care, and facilitate and improve the quality of documentation. The Resident Assessment Instrument/Minimum Data Set (RAI/MDS) especially developed for the care of elderly people, was used as a basis for individualized and documented nursing care. This study was carried out to compare nursing documentation in three nursing home wards in Sweden, before and after a one-year period of supervised intervention. The review of documentation focused on structure and content in both nursing care plans and daily notes. The greatest change seen after intervention was the writing of care plans for the individual patients. Daily notes increased both in total and within parts of the nursing process used, but reflected mostly temporary situations. Even though the documentation of nursing care increased the most, it was the theme medical treatment which was the most extensive overall. A difference was seen between computer-triggered Resident Assessment Protocol (RAP) items, obtained from the RAI/MDS assessments, and items in the nursing care plans; the former could be regarded as a means of quality assurance and of making staff aware of the need for further discussions. The RAI/MDS instrument seems to be a useful tool for the dynamic process in nursing care delivered and as a basis for documentation. The documentation should communicate a patient's situation and progress, and if staff are to be able to use it in their everyday nursing care activity, it must be well-structured and freely available. The importance of continuing education and supervision in nursing documentation for development of a reliable source of information was confirmed by the present study.