The efficiency of several chemical treatments in overcoming physiological seed dormancy, in Brachiaria brizantha seeds cv. Marandu, was verified in seeds recently harvested, processed and dried to 12% moisture content (wet basis). Seeds (spikelets) were individually hand-dehulled and the caryopsis were imbibed in vaccum for 10 minutes in different concentrations of potassium nitrate, thiourea and ethanol. In another assay, different time of imbibition in sodium hypochlorite was evaluated. Seeds which presented radicle protrusion, after 120 hours in a germination chamber at 30ºC, were considered germinated. Among the treatments, thiourea was the most efficient one in overcoming in Brachiaria brizantha physiological seed dormancy and potassium nitrate was the less efficient.