The role of quinolones in the maintenance and transfer of antibiotic resistance plasmids was investigated. Curing effect of eleven quinolones, at subinhibitory concentrations, was studied on Escherichia coli strains harbouring ten plasmids belonging to different incompatibility groups. R386, R446b and S-a were the only plasmids eliminated by all the quinolones at a rate between 0.5 to 16%. The best culture medium was human urine. A total inhibition of transfer of RP4 plasmid between two Escherichia coli strains was obtained with nalixidic and oxolinic acids and flumequin. A partial inhibition was observed with other quinolones.