Heracleum nepalense D Don. (Umbelliferae) is a small shrub having high glabrescent stem found instream banks in Sikkim. Various medicinal properties which include antidiarrhoeal, antiseptic,anti-influenzal etc. have been attributed for this plant in the traditional system of medicine inSikkim. In present investigation the methanol extract of roots of Heracleum nepalense was subjectedfor its effectiveness against both Gram-positive and Gram-negative bacteria causing diarrhoea.The roots extract was tested for its minimum inhibitory concentration (MIC) against both Gram-positive and Gram-negative organisms causing diarrhoea. Further, the zones of inhibitionproduced by the crude extract against few sensitive strains was measured and compared withthose of standard antibiotic ciprofloxacin. It is evident that the methanol extract is very activeagainst the bacteria causing diarrhoea at low concentrations. The antibacterial efficacy of the rootextract was found to decrease in the following order against different tested bacterial strains likeShigella dysenteriae, Escherichia coli, Shigella boydii, Vibrio cholerae, Salmonella typhimurium.