This study showed inAcholeplasma laidlawiithe possibility of transformation and fusion of protoplasts after induction by polyethylene glycol. Recombination in a genome of the resistance to chloramphenicol and neomycin has been obtained. Minimal inhibitory concentraiton of these antibiotics towards the recombined strain are identical to those measured with the parental strains. The most suitable experimental conditions have been studied. It appeared that the fusion, which is carried out more easily than the transformation, led to a higher frequency of recombination.[Translated by the journal]