Legumes are important to sustainable agriculture because of their N fixing ability and consequent reduced reliance on increasingly scarce oil resources. Our previous studies showed consistently higher intakes and milk yields when red clover silage replaced grass silage in dairy cow diets (Dewhurst et al., 2003). However, the increased intakes of a forage which contains higher levels of N led to a reduction in the efficiency of conversion of feed N into milk N (g/g) from around 0.25 to 0.20 or less. Maize silage has similar high intake characteristics, but its low N content and considerable starch content suggest that it would be highly complementary to red clover silage in terms of N-use efficiency. This study evaluated production and efficiency responses to mixtures of red clover and maize silages in comparison with perennial ryegrass silage.