Eleven various types of traditionally used Ethiopian medicinal plants have been screened for theirrnantimicrobial activity at the crude preparation level against six different bacteria, two Gram +vern(Bacillus cereus and Siaphyloccus aureus ) and four Gram -ve (Escherchia coli, Shigellarnboydii,Shigella jlexneri and Salmonella Iyphimunum). Of the tested crude preparations only tworn(Rula chalepellsis alldEchinops spp.) showed antimicrobial activity against B. cereus by the agarrnwell-plate diffussion assay. The effects of these crude preparations were found to be heatrndependent. Eight of the tested crude preparations at various concentrations by agar dillution assayrnwere found to be effective in or both of the Gram positive bacteria at various concentrations, asrnassessed by agar dilution assay. The l'vilC of Syzygillm guineense (0.312%) was the same for allrnsusceptible organisms (E. Cereus, S. aurellS, Sh. jlexneri and S. boydii). It appeared to bernbacteriocidal for S. aurellS, Sh. jlexneri and S. Boydeii). It appeared to be bactericidal for S.rn-------------------- - -'~ ---rnaurellS, Sh. jlexneri and S. boydii and bacteriostatic for B. cereus. All the active preparation foundrn-- .. ~- .-----rneffect by agar dillution assay, were found to be stable upon heating upto 121 0 C for 15 minutes.rnThe l'vilC of Carum copiticm, Rula chalepensis and Artemisia (!Ira against B. cereus was 5%. Itrnwas higher for Cymbopogon citra/us (10%) and lower for EchillOps spp.(0.625%) and Syzygillmrnguineense (0.312%). The l'vilC of Vernonia amygdalana was 5%. For S. aureus the l'vilC forthernlatter two plants was the same as for B. Cereus.rnOf the tested crude preparations, only Syzygium guineense appeared to bacteriocidal. The Ji[8Crnwas 1.25% for S. aureus and 5% for Sh. jlexneri and S. boydii. The crude preparations at thernl'vIBC killed all the population within 8 h in all the above mentioned organisms.rnBroth dillution assay was conducted to assess the antimicrobial effect of the crude preparationsrnconcentrations: Cal'1l11l copilicllm, Coriandrum salivllm, Echinops spp.at 10%; RlIta chalepensis,rnFonicu/um vulgare, Cymbopogon citratus, Vel'llonia amygdalina and Ginger officinale at 7%;rnArtemisia afi'a at 5% and Lipidium sativum at 2%. The results showed that eight of the crudernpreparations have reduced the final population of B. cereus by one to four log units as comparedrnto the control. On the other hand, ten of them were found to reduce the final population of S.rnaureus. Only one of the crude preparations had retarding effect on Sh. jlexneri, and two on Sh.rnboydii. None of them has inhibitory effect on E. coli and Salmonel/a Iyphimurium exceptrnSyzygium guineese that decreased the final population of Salmonella.