Summary(#br)An electroporation method using a Bio-Rad Gene Pulser has been optimized for introducing heterologous DNA into Kluyveromyces lactis yeasts. The plasmid pCR1, derived from a native Kluyveromyces plasmid, was used to transform K. lactis . This plasmid produces a wheat α-amylase and contains both the biosynthetic marker URAA and G418 resistance genes. Transformation was optimal at 4500 V/cm, 25 μF, and ∞ Ω with 0.2 μg plasmid DNA. Transformation efficiencies in the range 10 4 –10 5 transformants/10 7 cells/μg DNA were obtained.