In this paper, we review the literature on nursing workload in intensive care units (ICUs) and its impact on patient safety and quality of working life of nurses. We then propose a conceptual framework of ICU nursing workload that defines causes, consequences and outcomes of workload. We identified four levels of nursing workload (ICU/unit level, job level, patient level, and situation level), and discuss measures associated with each of the four levels. A micro-level approach to ICU nursing workload at the situation level is proposed and recommended in order to reduce workload and mitigate its negative impact. Performance obstacles are conceptualized as causes of ICU nursing workload at the situation level