The present paper reports on a study designed to investigate the validity and reliability of the Registered Nursing Care Contribution (RNCC) tool for assessing the level of nursing care required by care home residents. Care plan data from 186 residents in participating care homes were assessed by multiple assessors using the RNCC tool (i.e. care home registered nurses, a nurse researcher, an external care home expert and a nurses consultant). The Minimum Data Set (MDS) rating was used as a validated comparison. The findings from the study indicated that there were disparities between the RNCC and MDS bandings, and between different raters, with the external care home expert achieving the closest agreement with the MDS. This suggests that the use of the RNCC tool varies considerably according to the assessor, which also suggests that training of users is needed to ensure consistency and reliability. However, the difference between the outcomes of using the RNCC tool and the MDS suggests that assessment of nursing need may need to be re-examined to ensure validity.