Introduction: The use of medicinal plants as phytotherapy and preventive method is a millenary medicinal practice belonging to the most diverse cultures and is still practiced, especially in developing countries. The reasons for the use of these plant species are ease of availability and low cost, in addition to the fact that there are individuals who believe that natural products are less harmful to health than synthetic drugs. Objectives: The main objectives of this study were to evaluate the antimicrobial activity of ethanol extract from the bark of the cashew stem (Anacardium occidentale L.), against bacteria of medical importance and to perform preliminary phytochemical screening of the extract. Methods: The plant material was obtained commercially and then was submitted to extraction by the cold macerated method. Preliminary phytochemical screening was performed by colorimetry. Antimicrobial activity was evaluated using the disk-diffusion method. Results: The yield of the extract was 27.3 g. The following classes of metabolites were identified: phenols, tannins, flavonoids, flavoneones, leukoanthocyanins and quinones. As for antimicrobial assays, the extracts showed inhibition halos against Shigella flexneri bacteria in all concentrations tested (750 mg/mL= 10.9 mm; 850mg/mL=11.4 mm; 950 mg/mL=12.3 mm), and Enterococcus faecalis (750 mg/mL= 12.1 mm; 850mg/mL=12.3 mm; 950 mg/mL=12.2 mm). The extract did not present inhibition halos against pseudomonas aeruginosa bacteria. Final considerations: When analyzing the extracts it was possible to observe the antimicrobial potential of the bark of the cashew tree stem against bacteria of medical importance. Future studies are needed to determine the chemical profile of the extract, minimum injunction concentrations as well as perform cytotoxicity and genotoxicity tests. Vale ressaltar que, nas condições testadas o material vegetal mostrou-se promissor quanto a atividade antimicrobiana, principalmente avaliando as classes de metabólitos encontradas.
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