Eleven samples of eight European commercial varieties of winter rye were examined at eight polymorphic enzyme loci. Genotype frequencies fitted Hardy-Weinberg expectations at all loci in all samples studied. Of the total genetic diversity recorded at the 8 loci, only 7% was expressed between varieties. Allele frequency differences between varieties were, however, sufficient to allow a characterization of each variety by a specific set of allele frequencies. Using subsets of the original data, it could be demonstrated that all pairs of varieties but one still showed significant allozyme differences, when only 4 loci were screened in samples half the original size of 200 individuals. Even when only one locus was analyzed, all varieties but two were distinguishable, but this "diagnostic" locus was not identical in all pairwise comparisons.