Two viroids are known to infect stone fruit trees: Hop stunt viroid (HSVd) and Peach latent mosaic viroid(PLMVd). PLMVd has been found frequently in peach, and occasionally in plum, cherry and apricot germplasm from countries in Europe and Asia. Recent studies have reported it in very significant percentages in several Mediterranean countries. HSVd has been detected also frequently in the Mediterranean in several stone fruit species: i.e. apricot, peach, plum and almond. The application of recombinant DNA technology has permitted the use of molecular hybridisation and Polymerase Chain Reaction (PCR) for viroid detection. These techniques, combined with the application of an easy procedure for the extraction of total nucleic acids, the existence of non-radioactive PLMVd and HSVd. Specific probes and primers, are now used for routine diagnosis of stone fruit viroids. More recently, tissue-imprinting hybridisation, a technique that avoids sample extraction and only requires the direct transfer of the plant material (fruits, stem, cuttings, leaves) has been applied successfully to the detection oftheseviroids in stonefruits.