Rumenal samples of 21 sheep were examined bacteriologicaly from normal animals, impacted ones and after being treated from impaction. The microorganisms which were isolated were Pseudomonas sp., Staphylococcus sp., Hafnia, E.coli and Citrobacter sp. in normal animals, Pseudomonas sp., E.coli, Staphylococcus, Hafnia, Lacto-bacillus, Citrobacter and Pro videncia in impacted sheep and Pseudomonas, staphylococcus, E.coli and Hafnia sp.in treated sheep. The aforementioned organisms are. arranged in a chronological order. The role of aerobic bacterial flora is discussed.