Preparations of intact genomic DNA from 23 strains of Propionibacterium freudenreichii were compared by digestion with restriction endonucleases and subsequent transverse alternating field electrophoresis (TAFE). Seven restriction enzymes, AsnI, DraI, HpaI, SnaBI, SpeI, SspI, and XbaI, produced DNA fragments useful for strain comparisons. A characteristic restriction fragment pattern was identified for 18 of the 23 strains. Estimates for the genome size of the P. freudenreichii strains ranged from 1.6 x 10(6) to 2.3 x 10(6) base pairs based on the sum of fragment sizes obtained with restriction digests. Restriction endonuclease patterns resolved by TAFE are useful for strain identification.