Abstract: Plants used in folkloric medicine of Iranian native people were collected from Southeast regions of Iran. Methanol extracts were prepared and evaluated in a test against two strains of Escherichia coli. From 180 plant species in 72 families, 17 samples in 11 families showed anti-E. coli activity. At 20 mg ml-1 concentration, the most active plants with diameter of inhibition zones of 12 mm or more on both bacterial strains were Lawsonia inermis, Cinnamomum zeylanicum and Dianthus caryophyllus. Trigonella foenum-graecum, Cuminum cyminum, Alhagi maurorum, Apium graveolens, Colchicum luteum, Origanum majorana, Calendula officinalis, Nepeta racemosa and Coriandrum sativum were active only against E. coli (PTCC No. 1330) and Camellia sinensis and Anthemis nobilis were active only against E. coli (PTCC No. 1338). The lowest minimum inhibitory concentration found in Trigonella foenum-graecum as 0.46 mg ml-1. All of the active extracts were well stable at room temperature in DMSO: methanol (1:1, v/v) solvent and dry state up to 18 months and did not show any reduction of activity against the sensitive bacterial strains.