Species belonging to the Burseraceae family, especially of the genus Protium, are well known for producing fragrant oleoresins known in Brazil as breus. In this study, the physicochemical properties and antimicrobial activities of essential oils obtained from commercials samples of breu from the Brazilian Amazon were evaluated. Essential oils were extracted by hydrodistillation using a modified Clevenger apparatus and analyzed by gas chromatography/mass spectrometry (GC/MS) and GC/flame ionization detector (GC/FID). p-Cymene was the major constituent in all of the analyzed breu samples, with concentrations ranging from 21.9% to 51.9%, except for the white breu sample from Adolfo Lisboa Popular Market (ALPM), which contained α-pinene (22.7%). Other common monoterpenes were β-phellandrene, α-phellandrene, β-pinene, trans-dihydro-α-terpineol, α-terpineol and α-terpinene. The refractive indices ranged from 1.4769 to 1.4849 and the optical rotation ranged from -14.15° to +29.96°. The antimicrobial activity was low for all of the samples. The essential oil of black breu from ALPM was the only sample exhibiting antimycobacterial activity.