Experiments were conducted to evaluate digestible (dig) Lys requirements of male and female broiler chickens from 49 to 63 d of age. A dose-response diet consisting of corn, soybean meal, and corn gluten meal was formulated to be adequate in dig amino acid concentrations with the exception of Lys. L-Lysine . HCl was added to the dose-response diet to create 7 experimental diets. Concentrations of dig Lys of experimental diets ranged from 0.50 to 1.04% in increments of 0.09%. Variables measured consisted of standardized dietary Lys digestibility, feed intake, dig Lys intake, BW gain, feed conversion, mortality, abdominal fat weight and percentage, carcass weight and yield, and total breast meat weight and yield. In experiment 1, dig Lys of the dose-response diet was determined as 0.51% with cecectomized roosters. In experiment 2, dig Lys requirements of male broilers for BW gain, feed conversion, breast meat weight, and breast meat yield were 0.86, 0.88, 0.90, and 0.90%, respectively, based on 95% of the responses. From 49 to 63 d of age, male broilers optimized growth and meat yield measurements with approximately 3.0 g of dig Lys intake. In experiment 3, dig Lys requirements of female broilers were estimated as 0.79 and 0.83%, respectively, for BW gain and feed conversion. Digestible Lys intake necessary to optimize growth performance was 2.8 g/bird during 49 to 63 d of age. These results indicate that dig Lys requirements for male broilers were 0.87 and 0.90% of the diet, respectively, for growth performance and breast meat yield. Conversely, the dig dietary Lys requirement for females was 0.81% based only on growth performance.