A set of 175 chestnut trees was genotyped at 12 polymorphic isoenzyme gene loci. These trees belong to a  total of 13 presumed varieties with partially unknown origin. Only those varieties were studied, which consist of a minimum of five different individuals. Among a total of 175 trees, 110 different 12-locus genotypes were observed.
The genetic inventory of this material suggests that varieties with wide spatial distribution and  discontinous  occurrence reveal largest diversities. Within certain varieties, genetic similarity is evident while others consist  of individuals which are genetically very different. In several cases, genetic similarities seem to correspond to  morphological classifications. Genotyping helps to overcome problems in the identification of individual trees or varieties and may allow the determination of their origin. Results are compared with corresponding data from  Italian varieties.