The authors present a new multifactorial intensity and complexity of care model and meta-paradigm that is designed to examine costs, nursing work, and the variability in resource use across patients and environments. Relationships were observed among four key variables which included patient-nursing condition, medical condition, caregiver characteristics and the environment. Patient-nursing complexity and medical complexity are commonly measured by nursing diagnosis and DRG or Canadian case mix groupings (CMG) respectively. The complexities associated with the work environment had been the least previously studied factors. Environmental complexity factors include both supply and demand dimensions: scheduling and coordination of procedures, multiple and long procedures, and characteristics and composition of the caregiver team.