Single viroid sources were selected from the viroid collection maintained at IVIA to evaluate the field performance of infected trees. The assays were conducted in Corsica and Spain using the same viroid sources. Trifoliate orange seedlings infected with CEVd showed severe stunting, yellow blotching of the twigs and the bark scaling symptoms characteristic of the exocortis disease. Bark scaling and stunting symptoms were also observed when trifoliate orange was used as a rootstock. Trifoliate orange seedlings infected with three different sources of CVd-II (IIa, IIb and llc) showed characteristic bark cracks also observed when trifoliate orange was used as a rootstock. Only CVd-IIb and CVd-IIc variants induced cachexia symptoms on tangelo Orlando seedlings and on the scion of clementine trees grafted on trifoliate orange. The two apscaviroids, CVd-I and specially CVd-III caused a considerable reduction in size of trifoliate orange seedlings also observed when this species was used as a rootstock. No bark symptoms appeared associated with CVd-I and CVd-III infections. CVd-IV infection also caused bark cracking symptoms and size reduction on clementine trees grafted on trifoliate orange but these effects were not apparent on trifoliate orange seedlings. The results of these studies confirm that only CEVd induces the exocortis symptoms as initially described. The bark cracking symptoms and the reduced size resulting from infection with other citrus viroids should not be equated with "exocortis".