A total of 300 (250 clinically diseased and 50 apparent healthy) local breeds chickens (4 to 16 weeks old) were collected from different governmental and private farms at El-Fayoum and Beni Suef Governorates were employed. Bacteriological examination showed that 97 (32.3%) were positive for Campylobacter species. Those cases consisted of 88 isolates were recovered from 250 clinically diseased chickens and 9 isolates from 50 apparent healthy ones. Out of the examined 88 isolates of Campylobacter recovered from the diseased chickens, 45 were C. jejuni, 38 were C. coli and 5 were C. lardi with an incidence of 46.4 %, 39.2 % and 5.1% respectively. From apparent healthy chickens the 9 recovered isolates consisted of 6 C. jejuni and 3 C. coli. The recovery rate from different sites of all the examined chickens was almost equal from the Jejunum (44.3%) and caecum (43.3%), while it was in a descending rate from the liver (9.3%), gall bladder (2.1%) and heart blood (1.0%) as the number of Campylobacter species that were isolated from the jejunum, caecum, liver, gall bladder and heart blood was 43, 42, 9, 2, and one respectively. From diseased chickens, Campylobacter jejuni was mainly isolated from jejunum (29 isolates), followed by caecum (12 isolates), liver (3 isolates) and once from gall bladder contents. Campylobacter coli was mainly recovered from caecum (26 isolates), followed by jejunum (8 isolates), liver tissues (2 times), gall bladder and heart blood (1 isolate each). Campylobacter lari was recovered from jejunum (2 isolates) and liver tissues (3 isolates). In apparent healthy chickens, Campylobacter jejuni was isolated from jejunum (3 isolates), followed by caecum (2 isolates) and liver tissues (1 isolate), while Campylobacter coli was recovered from caecum (2 isolates) followed by jejunum (1 isolate). Experimental infection with Campylobacter jejuni showed that the first mortalities was recorded 6 days post infection in orally infected group and 4 days in intramuscularly infected group of chickens. Mortality rate was 20.0% (4/20) in orally inoculated group and 30% (6/20) in I.M. infected group. Re-isolation of the inoculated microorganism was recorded from the liver, caecum and jejunum from 3 (out of the 4 dead) orally infected chickens, and from. 5 (out of the 6 dead) I.M. inoculated ones. Rectal swabs that were collected from living chickens at the end of the experiment showed that C. jejuni was recovered from 3 living chickens of orally infected group and 2 from I.M. injected group. Experimental infection with C. coli produced 25.0% and 20.0% mortalities when inoculated I.M and orally respectively. The principal changes were in the form of distension of the intestinal tract. Intramuscular inoculation of C. jejuni and C. coli in a mixed form produced 35.0 % mortality rate with severely detectable pathological changes in the liver, accumulation of mucus and watery fluid in duodenal loop and hemorrhages in the intestinal tract. The mortality rate lowered to be 25.0% accompanied with severe dehydration and blood tinged duodenal mucosa when the two organisms were inoculated orally.