Traditionally, hospitals have coped with chronically high ICU census by building more ICU beds, but this strategy is unlikely to be tenable under future financial models. Therefore, ICUs need additional tools to manage census, inflow, and throughput.Higher ICU census, without compensatory surges in nursing capacity, is associated with several adverse effects on patients and providers, but its relationship to mortality is uncertain. Providers also discharge patients more aggressively during times of high census. Little's Law (L = λ W), a cornerstone of queuing theory, provides an eminently practical basis for managing ICU census and throughput. One target for improving throughput is minimizing process steps that are without value to the patient, e.g., waiting for a bed at ICU discharge. Larger gains in ICU throughput can be found in ICU quality improvement. For example, spontaneous breathing trials, daily wake-ups, and early physical/occupational therapy programmes are all likely to improve throughput by reducing ICU length of stay. The magnitude of these interventions' effects on ICU census can be startling.ICUs should actively manage throughput and census. Operations management tools such as Little's Law can provide practical guidance about the relationship between census, throughput, and patient demand. Standard ICU quality improvement techniques can meaningfully affect both ICU census and throughput.