The infectivity of four Campylobacter (C.) jejuni strains and one C. coli strain was evaluated by the reisolation rate from cloacal swabs after oral infection of chickens at four weeks of age. One strain did not colonize the digestive tract, another infected only a part of the experimental group and a third was excreted at a lower percentage in the first two weeks p.i. compared to the other two strains. In correlation to age, the excretion rate was highest in 7-week-old birds. In groups of 4 and 10-week-old chickens, the peak of the excretion rate appeared slightly delayed and on average, the excretion was lowest in 10-week-old individuals. A high correlation was found between the isolation rate of Campylobacters from cloacal swabs and from caecal contents.