Although significant progress in milk production efficiency has been achieved in recent years with the Holstein-Friesian breed, it is now realized that dairy cow breeding programmes with a primary focus on yield have resulted in increased levels of infertility, and reduced health and longevity. In contrast, Norwegian dairy cattle (NRF) have been bred within multi-trait selection programmes for approximately 25 years. As a consequence of the latter, the incidence of mastitis within Norway continues to decline, while fertility levels are increasing. In view of these positive trends within the NRF population in Norway, two studies were established to evaluate Norwegian dairy cattle under Northern Ireland conditions. The first of these was conducted at the Agricultural Research Institute of Northern Ireland (Keady and Mayne, 2002), while the second was established on 19 commercial dairy farms. The aim of the latter was to compare the production, fertility and health of animals of the NRF and Holstein-Friesian dairy breeds across a range of production systems.