Sixty-two piglets weaned at three weeks of age were allotted, in pairs, to four experimental diets (14 piglets to one diet and 16 piglets to each of the other three diets), and fed until 10 weeks of age. The diets were formulated to differ in digestible energy (DE) content with lysine: DE ratios of either 0,73 or 0,94 g lysine/MJ DE. The other dietary amino acids and protein were balanced according to the ideal protein concept. The piglets performed best on the diets with a high lysine: DE ratio, resulting in better performance (P ≤ 0,01) in all parameters. The most prominent improvement being the 42% for average daily gain (ADG), 32% for final mass and 25% for feed conversion. Feed costs per unit of gain were also lower (14%) for the piglets receiving the high lysine: DE ratio diets. Piglets receiving the high DE-level diets performed significantly better than piglets on the lower level of DE for all parameters except for feed intake and feed cost. The most prominent improvements are the 12% for ADG, 10% for final mass and 14% for feed conversion. Increasing dietary DE content above 14,5 MJ /kg for the high lysine: DE group had no significant (P >0,05) effect on piglet performance or on feed cost per unit of gain. However, a significant interaction (P ≤ 0,05) between DE level and lysine: DE level showed that both factors must be considered in determining the nutrient requirements of the early weaned piglet.