Background: Rhesus immunization is one of the main causes of isohaemolytic disease in newborns. In Denmark Rhesus anti-D-prophylaxis is administered to non-immunized Rhesus D negative women during pregnancy, after abortion and after childbirth, to prevent the disease. Despite this, several neonates are born with Rhesus haemolytic disease. Aim: The aim of this study was to determine the incidence of Rhesus haemolytic disease, the number of infants treated with intrauterine transfusion, exchange transfusion, top-up red blood cell transfusion, phototherapy and intravenous immunoglobulin in North Denmark Region during the period 2005-2014. Furthermore, to investigate whether the maximum plasma bilirubin concentration and the duration of the phototherapy decreased during the study period. Methods: In this retrospective cohort study, the ICD-10 revision codes system was used to identify the infants diagnosed with isohaemolytic disease in The North Denmark Region during the period 2005 – 2014. Data was extracted from journals from the Department of Paediatrics, the Department of Gynaecology and Obstetrics and the Blood Bank in Aalborg University Hospital (n = 100). 67 infants were included in the study and 33 were excluded because of a negative direct antiglobulin test, autoimmunization of the mother or missing information on direct antiglobulin test. Results: The total incidence of isohaemolytic disease was 1.22 ‰ of which Rhesus D immunization represented¬ 0.75 ‰. The incidence of Rhesus D immunization tended to be decreasing through the period. The number of immunizations with single and multiple antibodies was nearly equal. Infants with Rhesus D immunization were more severely affected than infants with other Rhesus immunization. Maximum plasma bilirubin concentration significantly increased while the average duration of the phototherapy was constant throughout the period, probably due to less aggressive treatment. Conclusion: The incidence of Rhesus D immunization tended to be decreasing during the period. The mean maximum plasma bilirubin concentration significantly increased while the average duration of the phototherapy was constant throughout the period.