Polymorphisms of a ribosomal DNA I region (ITS) have been analysed using a specific pair of primers, in order Co type fruitbodies and ectomycorrhizae of different truffle species. The identification of ectomycorrhizae was obtained by digestion of the PCR products using restriction enzymes. The results show that the strategy used is both suitable and sensitive to characterize the symbiotic fungi from few mycorrhized root tips.