Incidence and non-nutritional risk factors were estimated for necrotising enterocolitis in 2035 very low birth weight infants, admitted to 14 tertiary-level neonatal intensive care units in Lombardy, northern Italy. There were 62 necrotising enterocolitis cases, with an overall incidence of 3.1%. After adjustment for gestational age and centre, the risk factors were mechanical ventilation, patent ductus arteriosus, and late-onset sepsis, whereas surfactant treatment was associated with decreased risk. Significant variations in necrotising enterocolitis incidence among hospitals were found.