Breeding programmes for the Holstein-Friesian have historically focused on improved milk production with little emphasis on functional traits such as fertility or disease resistance. In contrast, Norwegian dairy cattle have been bred using a multi-trait selection procedure. Differences in selection procedures for the two breeds may have major effects on the efficiency of food use and partitioning of nutrients that may offset the potential advantages of improvements in functional traits. Recently, Yan et al., (2006) reported that Holstein-Friesian cows partitioned more energy into milk and less to body tissue than Norwegian cows. The objectives of the present study were to examine possible differences in nitrogen partitioning and the efficiency of N utilization between Holstein-Friesian and Norwegian dairy cows.