The rapid changes occurring in the management of the weaned pig, concurrent with rapidly increasing expectations of animal performance, suggest that diet formulations acceptable in the past may no longer suffice. This experiment focused on the lysine requirement of pigs from 28 to 56 days of age. A total of 240 pigs were randomly allotted from within weight groups to pens and one of six dietary treatments, representing total lysine: Digestible Energy (DE) ratios of 2.7, 3.0,3.3, 3.6, 3.9 and 4.9 g/Mcal. A significant linear but not quadratic response to dietary lysine was observed for both rate and efficiency of weight gain. The lack of a quadratic response indicated that the level of lysine at which animal performance would be maximized, must be either at or above the highest lysine level evaluated. We concluded that the lysine requirement for maximum performance in the rapidly growing early-weaned pig may be above currently accepted levels and require further review.