The recent increased use of out-of-parlour feeders for dairy cows has occurred for two main reasons: (1) convenience, including ease of rationing and saving labour; and (2) claims made for beneficial responses in milk yield and/or milk composition. The suggestions concerning improvements in milk composition arise from the effects of the increased frequency of concentrate feeding on certain rumen parameters. There is a reduced fluctuation in those parameters, with a maintenance of ruminai acetate production, which gives beneficial effects on milk fat production. Evidence from the literature indicates that an increased frequency of concentrate feeding does not increase the proportion of milk fat (on a weight basis) but merely rectifies a decrease in milk fat caused by a high concentrate to forage ratio. In trials conducted over 2 years, two groups of cows were offered equal amounts of concentrates from either a controlled out-of-parlour concentrate feeder to provide frequent feeding (O), or twice daily in the parlour (P). Group O out-yielded group P (25.1 v. 23.9, s.e. of difference 0.32** and 27.1 v. 25.4, s.e. of difference 0.56** kg milk/day) in years 1 and 2, respectively. The milk fat content (g/kg) for group O was consistently lower than for group P (36.5 v. 38.1, s.e. of difference 0.91, P = 0.10; 39.8 v. 42.6, s.e. of difference 1.47, P = 0.15) but the difference was not significant. The solids-not-fat content (g/kg) was significantly higher for group O in year 1 (89.9 v. 89.1, s.e. of difference 0.18***) but similar for the two groups in year 2 (90.9 v. 90.9, s.e. of difference 0.60, NS). Overall, the yields of milk fat on the two treatments were similar but the yields of all other milk constituents were increased significantly with out-of-parlour feeding.