In its first week of age 24 males calves from a dual purpose herd were implanted as follows: (1) 6 with estradiol17- B (Compudose-200l, (2) 6 with zeranol (Ralgro) reimplanted 90 days later, 6 with a single dose of zeranol, and (4) 6 calves as control group. The weaning weight at eight months of age, and the average daily gains were 135.3, 138.1, 126.0, and 124.0 kg and OA 18, OA08, 0.368 and 0.355 kg/day for groups 1, 2,3 and 4 respectively (P < 0.05). The better perfomance of the implanted groups was asigned to a greater feeding efficiency, due to a diet made of milk and grass exclusively. At 10, 52, 100, 134, 158, 294 y 253 days of age the response is of parabolic type in relation to the control group. The largest response are obtained with treatments (1) and (2). The treatment with zeranol alone showed a sudden faII at 120 days of age (end of its effect), and along the experiment its perfomance was low and erratic probably due to endocrine disadjustement. From the biological and economic point of view the anabolics are convenient to rise male calves coming from herds of dual purpose in this country.