The UK Neonatal Staffing Study (UKNSS) investigated the relation between the directly alterable organisational characteristics of volume, staffing levels and workload and risk-adjusted hospital mortality and morbidity in this prospective UK-representative study. To assess whether risk-adjusted mortality and morbidity outcomes of UK neonatal intensive care are related to: differences in primary organisational characteristics of volume, medical and nurse staffing levels, and workload; adherence to national standards of service provision. The cross-sectional approach examined whether overall average unit workload during the study period was related to the primary outcomes. The primary outcomes were assessed in relation to the primary organisational characteristics: death before hospital discharge or planned deaths at home, major brain damage on cerebral ultrasound. The longitudinal approach aimed to examine whether variations in workload and infants' exposure to variations within each unit during the study period were related to the primary outcomes.