Knowledge of bacteriophage ecology in vegetable fermentations is essential for developing phage control strategies for consistent and high quality of fermented vegetable products. The ecology of phages infecting lactic acid bacteria (LAB) in commercial sauerkraut fermentations was investigated. Brine samples were taken from four commercial sauerkraut fermentation tanks over a 60- or 100-day period in 2000 and 2001. A total of 171 phage isolates, including at least 26 distinct phages, were obtained. In addition, 28 distinct host strains were isolated and identified as LAB by restriction analysis of the intergenic transcribed spacer region and 16S rRNA sequence analysis. These host strains included Leuconostoc, Weissella, and Lactobacillus species. It was found that there were two phage-host systems in the fermentations corresponding to the population shift from heterofermentative to homofermentative LAB between 3 and 7 days after the start of the fermentations. The data suggested that phages may play an important role in the microbial ecology and succession of LAB species in vegetable fermentations. Eight phage isolates, which were independently obtained two or more times, were further characterized. They belonged to the family Myoviridae or Siphoviridae and showed distinct host ranges and DNA fingerprints. Two of the phage isolates were found to be capable of infecting two Lactobacillus species. The results from this study demonstrated for the first time the complex phage ecology present in commercial sauerkraut fermentations, providing new insights into the bioprocess of vegetable fermentations.