Genetic variation in 5 natural stands of Quercus robur L. in Finland was analysed electrophoretically for 13 isozyme loci. Stands were on average polymorphic at 49.2% of the loci, with 2.1 alleles per locus. Observed heterozygosities, ranging from 13.6% to 16.9%, were slightly lower than estimates reported for German stands. The majority of the species’ genetic variation was found within each studied stand, and only 5.5% was between stands. Mean genetic differentiation (∂) was the same as that found in the primary range of the species, but the differentiation estimates (D) for single Finnish population were more variable.