More than 20% of the world's biodiversity is located in Brazilian forests and only a few plant extracts have been evaluated for potential antibacterial activity. In the present study, 705 organic and aqueous extracts of plants obtained from different Amazon Rain Forest and Atlantic Forest plants were screened for antibacterial activity at 100 microg/ml, using a microdilution broth assay against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli. One extract, VO581, was active against S. aureus (minimum inhibitory concentration (MIC)=140 microg/ml and minimal bactericidal concentration (MBC)=160 microg/ml, organic extract obtained from stems) and two extracts were active against E. faecalis, SM053 (MIC=80 microg/ml and MBC=90 microg/ml, organic extract obtained from aerial parts), and MY841 (MIC=30 microg/ml and MBC=50 microg/ml, organic extract obtained from stems). The most active fractions are being fractionated to identify their active substances. Higher concentrations of other extracts are currently being evaluated against the same microorganisms.