During a virus survey in autumn 2007 and spring 2008 of two Tunisian olive mother blocks, 175 olive samples were collected from 19 different cultivars and tested by RT-PCR for the presence of Arabis mosaic virus (ArMV), Cherry leaf roll virus (CLRV), Cucumber mosaic virus (CMV), Olive latent ringspot virus (OLRSV), Olive latent virus 1 (OLV-1), Olive latent virus 2 (OLV-2), Olive leaf yellowing-associated virus (OLYaV) and Strawberry latent ringspot virus (SLRSV), using specific sets of primers. The PCR-negative samples were also subjected to dsRNA and mechanical transmission tests. PCR results indicated that c. 86% of the trees were infected with at least one virus, whereas visible bands were shown by 3 of 24 PCR-negative samples in dsRNA analysis. OLYaV was the most prevalent virus (49.1%), followed by OLV-1 (34.3%), CMV (25.7%), OLRSV (16.6%), CLRV (13.1%), SLRSV (7.4%) and OLV-2 (6.9%), whereas ArMV was not detected. Very high infection rates were found in the two main oil cvs. Chemlali (84.6%) and Che´toui (86.9%).