Phenol-extracted DNA from mycoplasma virus L2 was able to transfect Acholeplasma laidlawii in the presence of polyethylene glycol. Transfection was sensitive to DNase and was most efficient with 36% (wt/vol) polyethylene glycol 8000 and cells in logarithmic growth. Virus production by the transfected cells was similar to that of the cells infected by intact virus. L2 DNA transfected A. for chromosomal markers (16). PEG-mediated transfection of protoplasts with bactriophage DNA has been reported in Streptomyces sp. (15) and in Streptococcus sp.