Formulating diets to match more closely the requirements of the pig for amino acids results in diets which are lower in crude protein (CP) than conventional commercial diets. The lower intake of nitrogen (N) which is concomitant with these diets results on lower N excretion. The excretion of excess N requires energy and previous nutrient balance work undertaken at Terrington (Lee and Kay, 1998) indicated that the ‘energy sparing’ effect of the reduced crude protein diets can be utilised by reducing the digestible energy (DE) content of reduced CP diets whilst at the same time maintaining the level of N retention. The objective of this work was to determine the performance carcass characteristics and slurry characteristics of growing/finishing pigs given reduced CP/DE diets.