An experiment was conducted to determine the optimal standardize ileal digestible (SID) Lys level for growth performance of nursery pigs. A total of 980 pigs (PIC 337 × Camborough; initial BW = 5.4 kg), placed in pens with 28 pigs each, were used in a 42-d trial. There were 5 treatments consisting of 1.15, 1.25, 1.35, 1.45, or 1.55% SID Lys. Experimental diets were fed from d 0 to 21 followed by a common corn-soybean meal based diet (1.30% SID Lys) from d 21 to 42. Pigs were weighed weekly to calculate ADG, ADFI, and G:F. Data was analyzed with SAS MIXED procedure. From d 0 to 21, increasing the SID Lys level resulted in a linear (P < 0.01) ADG, G:F, and BW improvement. Because of the linear nature of the response, the breakpoint could not be determined. From d 21 to 42, when pigs were fed a common diet, linear (P < 0.05) ADG and G:F responses were observed; pigs previously fed the lower SID Lys levels had improved performance. This compensatory response resulted in no evidence for differences (P > 0.10) in overall (d 0 to 42) ADG and final BW, although there was a linear (P = 0.004) G:F improvement.