To determine the effect of adding Ractopamine (RAC) and Threonine:Lysin ratio (Thr:Lys) on the productive yields, an experiment during 28 days was made. 42 pigs of approximately 72,4± 2,3 kg were used in which the effect of two levels of RAC was evaluated (5 and 10 ppm) and three relate Thr:Lys (0,60; 0,65 and 0,70) in the diet on the consumption of daily food (CDF), the daily weight gain (DWG), daily lean fat-free tissue gain (DLFFTG), and also, the efficiency (Ef) was expressed as DLFFTG in function of CDF. A randomized experimental block design, in a 2 x 3 factorial arrangement and a repeated-measures analysis over time were made. All the variables were measured in each animal 14 and 28 days after initiate the diet supply. The mean/animal/days values of all the variables presented interactions. In general it was observed that high levels of Rac had a better acting with low or mean levels of Thr:Lys while the low levels of Rac had better results with high levels of Thr:Lys. For this reason, differences among variables with two levels of Rac are due to nutritional handling (Thr:Lys ratio), since this factor influences the magnitude of the answer. From the productive point of view, the combination to recommend is 10 ppm of Rac and Thr:Lys 0,6.