Intensive care nursing allocation seemingly has been a negotiated solution to a never ending battle: an arbitrary nursing/patient ratio. To correct this deficit, a prospective study was proposed to quantitate the time duration of sufficient intensive care to match the severity of illness. A comprehensive list of all nursing actions was compiled and timed. Thereafter, frequencies were observed according to global classifications: serious, critical, or crisis. A simple classification system separates the hourly requirement: serious = 2:1 patient/nurse ratio, critical = 1.0:0.75 full time nursing, and crisis = 1.0:1.2 patient/nurse ratio (or single nurse requires assistance). The increased requirements are created by increased need for ICU skills: vital signs = 1 hour for serious patients, 4 hours for critical, and a maximum of 10 hours for crisis patients (90% crisis patients has pulmonary artery and arterial catheters). Other categories of increased nursing time reflect ventilatory support, increased number of continuous and intermittent medications, etc. Global assessment (serious, critical, or crisis patient status) can be quantitated in terms of nursing hours actually required. Objective, rational, and variable patient/nurse ratios can be easily and accurately achieved in this manner. Staffing requirements and allocation of positions can be objectively quantitated.