Secondary data are increasingly incorporated into nursing research studies, as nurses seek to capture and address the complexity of patient care There is, however, little discussion in methodological literature about this type of data, the meaning is taken for granted and the data are regarded as simple sources of information, which are convenient and cost-effective This approach denies the social meaning of the data, and is likely to lead to misinterpretation of the content This paper discusses these analytical issues with reference to a research study which used secondary data (nursing care plans) in an examination of the ways in which nurses assess their patients Using this data led to an increased understanding of the social world in which assessment took place