Plasmids pCG76, pCG83, pCG110 and pCG111 were transferred from multiresistant Escherichia coli strains of avian intestinal origin to E. coli K12. They were found to be compatible with reference plasmids of several incompatibility groups, except RP4. This incompatibility with RP4 is a proof that they belong to group incP. Other plasmids of this group were found in E. coli strains isolated from the feces of hens in two different breeding flocks. The incidence and the importance of this plasmid group in the intestinal bacteria of animals are presently investigated.