Phytoplasmas are wall-less bacteria associated with many diseases of cultivated and wild plants. They are transmitted by phloem-sucking insects, mainly leafhoppers, planthoppers and psyllids (Hemiptera, Homoptera). The detection and identification of phytoplasmas in their insect vectors is needed to design rational control strategies of phytoplasma-associated diseases. The application on vector insects of methods based on microscopy, serology and particularly on DNA technology, such as molecular hybridization, PCR and post-PCR analyses, are reviewed. The results obtained with phytoplasma-specific molecular tools on vectors are illustrated with particular emphasis on the identification of new vector species, estimation of infectivity of field populations, evaluation of the influence of different factors on transmission capability and isolation and functional characterization of phytoplasmas from infected insects.