Objectives: Nurse stafﬁng costs represent approximately 60% of total intensive care unit costs. In order to analyse resource allocation in intensive care, we examined the association between nurse stafﬁng costs and two patient classiﬁcation systems: the nursing activities score (NAS) and nine equivalents of nursing manpower use score (NEMS). Research methodology/design: A retrospective descriptive correlational analysis of nurse stafﬁng costs and data of 6390 patients extracted from a data warehouse. Setting: Three intensive care units in a university hospital and one in a regional hospital in Norway. Main outcome measures: Nurse stafﬁng costs, NAS and NEMS. Results: For merged data from all units, the NAS was more strongly correlated with monthly nurse stafﬁng costs than was the NEMS. On separate analyses of each ICU, correlations were present for the NAS on basic costs and external overtime costs but were not signiﬁcant. The annual mean nurse stafﬁng costfor1%ofNASwas20.9–23.1eurosintheunits,whichwascomparableto53.3–81.5 eurosfor1NEMS point. Conclusion: A signiﬁcant association was found between monthly costs, NAS, and NEMS. Cost of care should be based on individual patients’ nursing care needs. The NAS makes nurses’ workload visible and may be a helpful classiﬁcation system in future planning and budgeting of intensive care resources.