Porphyromonas gingivalis, is one of the bacteria associated with periodontal disease that has been related to coronary artery disease, pneumonia, and preeclampsia. The purpose of this study was to evaluate the methanol extract of roots of Krameria ramosissima against P. gingivalis (ATCC 53978), its cytotoxic activity in human fibroblasts (ATCC CRL-7222 274.T Hs) and its mutagenic potential using the Ames test. Asessed concentrations were 500, 400, 300, 200, 150, 100, 75 and 50 μg/mL, with the minimum inhibitory concentration being of 300 μg/mL. By column chromatography were obtained 14 fractions of which the fractions 7 and 9 showed higher inhibitory activity (P