In order to verify the effect of storage temperatures and of high temperatures on Brachiaria brizantha cv. Marandu seed dormancy, just harvested seeds were cleaned and dried in a forced air oven to 12% of moisture content (wet basis). Three sub-samples were packed in paper bags and stored for nine months at 4ºC, 15ºC and 30ºC. An another essay, the high temperature effect on the seeds was verified seed samples were placed in paper bags and exposed to 50, 60 and 70ºC in dry condition and to 42ºC in wet condition (accelerated aging) for: zero, 24, 48, 72 and 96 hours. After the respectives treatments, seeds were dehulled and vacuum imbibed in trizma-base buffer solution at 10mM and pH 6.0. Seeds presenting radicle protrusion after 120 hours on germination chamber were considered germinated. It was verified that lower temperatures (4°C) were able to extend the dormancy period during the storage. It was also observed that high temperatures (70°C/72 hours) may be used to overcome physiological seed dormancy in Brachiaria brizantha seeds.