The introduction of fully controlled out-of-parlour concentrate dispensers has brought new opportunities to concentrate feeding for dairy cows. While there may be a number of possible justifications for their use on an individual farm, it is likely that their effect on milk output and efficiency of concentrate use, will be a major factor when assessing their potential use. It has been argued that their ability to not only allow accurate concentrate rationing for each individual animal, based on milk yield, but also the fact that they can increase the frequency with which readily degradable materials, such as concentrates, are fed will provide nutritional benefits which will result in improved animal performance. In contrast the simple flat rate feeding approach implies a uniform feed input to all animals irrespective of stage of lactation or milk yield and also is generally operated on no more than two or three feeds over the 24 hour period. The purpose of the present study was therefore to compare two systems of concentrate feeding involving either the use of an out-of-parlour feeder, in which concentrates were allocated according to the milk yield of the individual animal, or the flat-rate approach. In view of the possibility that there could be an interaction between feeding system and total concentrate input both systems of feeding were compared at two levels of concentrate feeding.