This study was initiated to isolation and identification of probable bacterial causes in the fecal samples of newly born calves suffering from enteritis in some farms of Assiut Governorate A total number of 80 calves were subjected to the study. These animals were randomly selected from some Assiut farms. Twenty-five calves were considered as the control group. These animals aged from one day to one month suffering from sever diarrhea, increase of body temperature (average 40.5ºC) and increase in heart rate. Some calves have had loss of appetite, dehydration and dullness. Fifty- five diseased calves were classified according to its age into four groups, the first group included fourteen calves aged 1-5days old, second group included sixteen calves aged from 6-10days old, third group included twelve calves aged from 11-15days old and the fourth group included thirteen calves aged from 16-30days old. The bacteriological examination reveald that the incidence of enteric bacterial isolates in apparently healthy calves was 72% and it was lower than in diseased calves (100%). It is clear that the incidence of enteric bacteria was 100% in all fecal samples. There were a wide range of bacteria isolates from feacal samoles of both apparently healthy and diseased calves. The isolates were Escherichia coli (O157) from diseased calves in all four groups with different percentages (64.28%, 50%, 33.33% and 23.07%) respectively, Salmonalla typhimurium (35.71%, 18.75%, 25% and 7.60%) respectively and Clostridium perfringens (78.57, 56.25, 58.33 and 61.53) respectively respectively. It was noticed that Clostridium perfringens was recorded with the highest incidence. Moreovere, diarrhea become sever and have offensive odur in calves occurred mainly when a combination between the three bacteria (E. coli (O157), Salmonella typhimurium and Cl.perfringens). It was noticed that younger calves were more susceptible than the older ones. Pathoenicity test in mice revealed that E. (O157) 87% were highly virulent strains followed by Salmonella typhimurium 75% while Cl. perfringens were lower in their virulence (62.5%)