Introducción: La producción ovina es el principal recurso de familias que habitan a gran altura. Sin embargo, presenta una eficiencia reproductiva pobre en relación con lo registrado a nivel del mar. La hipoxia hipobárica propia de ambientes a gran altura produce estrés oxidativo, lo que también produce efectos perjudiciales en el aparato reproductor. Bajas tasas de fertilidad, desarrollo intrauterino y bajos pesos al nacimiento son algunos de los efectos perjudiciales de la gran altura. La terapia antioxidante en ovejas mantenidas en la altura ha mostrado reducir el daño oxidativo causado por la hipoxia e incrementar la capacidad reproductiva. Por esta razón, se evaluó si la suplementación con vitaminas antioxidantes C y E atenúa los efectos perjudiciales del estrés oxidativo causado por hipoxia en la función reproductiva de carneros expuestos a la altura por corto y largo tiempo. Materiales y Métodos: Se utilizaron carneros nativos y mantenidos a nivel del mar (BB; n=20); nativos del nivel del mar, expuestos a la altura (BA; n=50); nativos de la altura, mantenidos en la altura (AA; n=50). La mitad de los animales de cada grupo fueron suplementados diariamente con 600 mg de vitamina C y 450 UI de vitamina E, vía oral, durante 240 días. Se analizaron las poblaciones celulares presentes en el epitelio seminífero, la morfología espermática en el eyaculado y el estatus antioxidante del plasma seminal. Resultados: La suplementación con vitaminas evitó y/o amortiguó la reducción de la población de espermatogonias, la reducción de la altura del epitelio seminífero y el diámetro tubular, la disminución de la capacidad antioxidante total y redujo el grado de arresto espermatogénico al día 30 en carneros no adaptados a la altura. Sin embargo, no tuvo efectos sobre la morfología espermática y las enzimas presentes en el plasma seminal de carneros expuestos a gran altura por corto y largo tiempo. Conclusión: La suplementación con vitaminas antioxidantes favorece la espermatogénesis y la capacidad antioxidante total del plasma seminal de carneros no adaptados a la altura en el corto plazo. / Introduction: The sheep production is the main resource of families living at high altitude. However, has a poor reproductive efficiency in relation to that recorded at sea level. Hypobaric hypoxia at high altitude environments produces oxidative stress, which leads to detrimental effects on the reproductive system. Low fertility rates, low intrauterine development and low birth weights are some of the damaging effects of exposure to high altitude. Therapy with antioxidant in ewes maintained at high altitude has been shown to reduce oxidative damage caused by hypoxia and increase reproductive capacity. For these reasons, supplementation with antioxidant vitamins C and E was evaluated in its capacity to attenuate the oxidative deleterious effects on reproductive function in rams exposed to high altitude for short or long periods. Materials and Methods: Three groups of rams were evaluated, rams born and kept at sea level (BB, n = 20); rams born at sea level and exposed to high altitude (BA; n = 50); born and kept at high altitude (AA; n = 50). Half of the animals in each group were daily supplemented with 600 mg of vitamin C and 450 IU of vitamin E, orally, for 240 days. The cell populations present in the seminiferous epithelium, the sperm morphology in the ejaculate and the antioxidant status of seminal plasma were analyzed. Results: Oral supplementation with vitamins C and E prevented and / or softened the reduction of the spermatogonial population, the reduction of the height of the seminiferous epithelium and the tubular diameter, the decrease of the total antioxidant capacity and reduced the degree of spermatogenic arrest at day 30 in rams not adapted to high altitude However, it did not have effects on sperm morphology and enzymes present in the seminal plasma of rams exposed at high altitude for a short and long periods. Conclusion: Supplementation with antioxidant vitamins favors the spermatogenesis and the total antioxidant capacity of the seminal plasma of rams not adapted to high altitude in the short term. / Introduction: The sheep production is the main resource of families living at high altitude. However, has a poor reproductive efficiency in relation to that recorded at sea level. Hypobaric hypoxia at high altitude environments produces oxidative stress, which leads to detrimental effects on the reproductive system. Low fertility rates, low intrauterine development and low birth weights are some of the damaging effects of exposure to high altitude. Therapy with antioxidant in ewes maintained at high altitude has been shown to reduce oxidative damage caused by hypoxia and increase reproductive capacity. For these reasons, supplementation with antioxidant vitamins C and E was evaluated in its capacity to attenuate the oxidative deleterious effects on reproductive function in rams exposed to high altitude for short or long periods. Materials and Methods: Three groups of rams were evaluated, rams born and kept at sea level (BB, n = 20); rams born at sea level and exposed to high altitude (BA; n = 50); born and kept at high altitude (AA; n = 50). Half of the animals in each group were daily supplemented with 600 mg of vitamin C and 450 IU of vitamin E, orally, for 240 days. The cell populations present in the seminiferous epithelium, the sperm morphology in the ejaculate and the antioxidant status of seminal plasma were analyzed. Results: Oral supplementation with vitamins C and E prevented and / or softened the reduction of the spermatogonial population, the reduction of the height of the seminiferous epithelium and the tubular diameter, the decrease of the total antioxidant capacity and reduced the degree of spermatogenic arrest at day 30 in rams not adapted to high altitude However, it did not have effects on sperm morphology and enzymes present in the seminal plasma of rams exposed at high altitude for a short and long periods. Conclusion: Supplementation with antioxidant vitamins favors the spermatogenesis and the total antioxidant capacity of the seminal plasma of rams not adapted to high altitude in the short term. / Financiamiento: Proyecto Fondecyt 1130181