Genetic diversity of "bois noir" phytoplasma (BNp) isolates was determined by PCR-RFLP of the stolbur specific stol-1H10 gene encoding a putative membrane protein. BN-infected grapevines were collected from the most representative Italian and French wine producing regions. Weeds and vectors collected in infected vineyards from different Italian regions were also analysed for BN characterization. Size polymorphism of stol-1H10 gene was obtained from PCR assays. Twelve different RFLP patterns were detected in BNp grapevine isolates, one in Urtica dioca and four in Convolvolus arvensis isolates. Hyalesthes obsoletus BNp isolates with two prevalent RFLP profiles were detected in grapevines and in herbaceous hosts from the same vineyards. Stol-1H10 represents a useful non-ribosomal marker to type BNp in plant and insect hosts.