Home health care today is challenged by a shift from an acute to a chronic health-care model, moving the focus of care from the hospital to home-care setting. This increased focus on care at home emphasizes the need for an efficient, effective, and transparent management of home health care. However, it is not precisely known what home-care nurses do; what kind of care is received by patients; what the performance of home nurses is; and what the impact of the increasing need for home nursing is on the current and future role of home nurses. In this respect, it is necessary to gain a clear insight into the activity profile of home nurses, but there is no gold standard to measure their activities. This study reports on the development and psychometric testing of the '24-hour recall instrument for home nursing' to measure the activity profile of home nurses. Five home nurses in Belgium, simultaneously with the researcher, registered the performed activities in a total of 69 patients, using the 24-h recall instrument for home nursing. The validity and the interrater reliability of this instrument were high: the proportions that observed agreement were very high; the strength of kappa agreement was substantial to almost perfect; the prevalence index showed great variety; and the bias index was low. The findings in this study support the validity evidence based on test content and the interrater reliability of the 24-h recall instrument. This instrument can help to shape practice and policy by making the home nursing profession more transparent: a clear insight into the kind of care that is provided by home nurses and is received by the patients in primary care contributes to the development of a clear definition of the role of home nurses in health care.