The production of complete cDNA libraries from minimal amounts of starting material (i.e., mRNA) is a major challenge for cDNA cloning technology. This paper reports the cDNA cloning efficiencies of electroporation and in vitro packaging. These two methods produce a tremendous number of recombinant clones (greater than or equal to 1 x 10(8) clones/micrograms cDNA) although electroporation generates more clones at nearly all cDNA concentrations used in a ligation reaction.