Myrtaceae family is one of the largest and most important of the Brazilian flora. The leaves of most species of this family contain considerable amounts of volatile substances, which make them particularly rich in essential oils. In folk medicine the leaves of many species of this family are used in the most different diseases. Psidium striatulum DC species is a variety of this family, popularly known as araçá or araçari in the Amazon region and the best known are guava, guava bush and araçá mirim. In folk medicine they are used in the treatment of diarrhea and infections that cause harm to human health. Thus, this work aims to characterize the chemical profile and biological evaluation of essential oil of the fresh leaves of Psidium striatulum DC from Roraima, Brazil. The leaves were collected in the municipality of Boa Vista-RR, on the margin of Rio Branco and submitted to a hydrodistillation process, in a Clevenger, Spell brand double condenser type device for a 2 hour interrupt period. Identification of constituents of the essential oil was performed by comparing the mass spectra obtained by the GC-MS spectra with the NIST11 library and also by comparing the Kovats indexes calculated by GC-FID and literature data. The essential oil chromatogram of P. striatulum fresh leaves had 20 peaks. Among the major compounds identified are humulene (13%), ?-copaene (8.4%), 1.8-cineole (8.1%), aromadendrene (6.3%) and ?-terpinenol (2.1%), globulol (5.5%), ß-caryophyllene (5.2%), ß-cadinene (4.1%). Microbiological tests of the essential oil at 250 µg mL-1 were performed against Staphylococcus aureus, ATCC 29212 (47.63 ± 1.58%); Bacillus cereus, ATCC 11778 (62.15 ± 0.10%); Escherichia coli, ATCC 25922 (0.24 ± 0.05%); Salmonella typhimurium, ATCC 14028 (64.03 ± 0.83%) and C. albicans (7.33 ± 2.50%) and showed moderate inhibitory activity for the enzyme AChE (53.12 ± 0.53%). The results in vitro of the essential oil indicate that they are important in the inhibition of microorganisms, Alzheimer's and can be used in nature form, in the form of tea infusion or as aromatic condiment.