A reference library of ITS PCR/RFLP profiles was collated and augmented to evaluate its potential for routine identification of domestic brewing yeast and known 'wild' yeast contaminants associated with wort, beer and brewing processes. This library contains information on band sizes generated by restriction digestion of the ribosomal RNA-encoding DNA (rDNA) internal transcribed spacer (ITS) region consisting of the 5.8 rRNA gene and two flanking regions (ITS1 and ITS2) with the endonucleases I, III, I and includes strains from 39 non- yeast species as well as for brewing and non-brewing strains of . The efficacy of the technique was assessed by isolation of 59 wild yeasts from industrial fermentation vessels and conditioning tanks and by matching their ITS amplicon sizes and RFLP profiles with those of the constructed library. Five separate, non-introduced yeast taxa were putatively identified. These included species, which were associated with conditioning tanks and species isolated from fermentation vessels. Strains of the lager yeast could be reliably identified as belonging to either the Saaz or Frohberg hybrid group by restriction digestion of the ITS amplicon with the enzyme III. Frohberg group strains could be further sub-grouped depending on restriction profiles generated with I.