'Candidatus Phytoplasma solani' is a bacteria without a cell wall, which is an obligatory parasite of plants. It causes diseases in many plants, for example: Bois Noir on grapevine. By sequencing nested polymerase chain reaction products of tuf, secY and stamp genes, we determined the molecular diversity of 'Ca. P. solani' strains isolated from grapevines. By analyzing their occurrence in Slovenia on a geographical and time scale and then comparing the results with similar analysis in Europe, especially in surrounding countries, we determined possible pathways by which spreading of Bois Noir grapevine disease, between Slovenia and its neighbouring countries, can occur.