Studies in the UK on continuously stocked swards dominated by perennial ryegrass show that both net herbage production and lamb output per hectare are maximised when herbage mass is maintained at 1200-I 500 kg OM/ha (3-5 cm surface height) during the main season of growth. The use of this information to define sward management objectives is outlined, and the incorporation of these objectives into the spring and summer phases of a grassland sheep enterprise is illustrated