In this study evaluated the antibacterial and allelopathic activities of ethyl acetate extract and its fractions F1L, F1M, F1N, and F1R F1O Miconia caudata (Bonpl.) DC. in the family Melastomataceae against seedlings of lettuce (L. sativa). The ethyl acetate extract was separated on chromatographic column packed with DIAION HP-20, using gradient elution system stepwise water-isopropanol, obtaining 20 fractions which were monitored by measuring the absorbance at 280 nm and using layer chromatography fine criteria were used to select the five fractions were finally evaluated. Additionally, tests were performed to identify chemical characteristics of secondary metabolites. The antibacterial activity was determined by agar diffusion method in wells against E. coli, S. aureus and P. aeruginosa. The extract and fractions showed no positive results at the concentrations tested. Each of the assays was performed in triplicate. Allelopathic activity assay was performed for seven days in each fraction, with the result that the F1M fraction showed a growth stimulating effect on hypocotyl with a maximum on the seventh day value of 54.39%. By chemical tests it was found that this fraction is present type secondary metabolites condensed tannins. Fractions F1L, F1N and F1O behaved similarly allelopathic activity, inhibiting the growth of the seedling hypocotyl L. sativa. The F1R fraction showed an inhibitory effect on seedlings, much higher than that observed in the other fractions tested, with maximum values on day one and two of assay 93.78% 86.67% and, respectively. To this fraction F1R chemical tests were performed which indicated the presence of sesquiterpene lactones which may be involved in the activity allelopathic presented. The F1R fraction was selected to be subjected to fractionation due to allelopathic activity observed growth stimulation in this, for this purpose used a chromatographic column packed with silica gel. Separation process six fractions were obtained, the chemical were tested for sesquiterpene lactones in thin layer chromatography.