Was made biological tests with hidroalcoolic extract of Pfaffia glomerata roots. In sleeping time test in mice, the extract was administered in several doses acutely and after 10 and 30 days of oral treatment. In the antibacterial analysis, the effect of the extract was evaluated on Staphylococcus aureus, Escherichia coli, Bacillius subtilis and Pseudomonas aeruginosa. In the sleeping time, in the acute model it was obtained depressive effects for the doses of 500 and 1000 mg/kg; in the chronically treated animals, to the 10 days of treatment it was obtained depressive effect with 50 mg/kg and stimulating effect with 500 mg/kg; to the 30 days of treatment other stimulating effect happened with the dose of 1 mg/kg. In the antibacterial test growth inhibition was not observed of none of the samples of the bacteria in the largest concentration of 1000μg/ml of the extract. It is ended that the extract of the roots of P. glomerata doesn't have antimicrobial effect and it seems to promote interference on the sleep of animals in a two-phase way in agreement with the doses and times of treatment.