A viroid etiology for citrus gummy bark (CGB) disease of sweet orange is supported by the similarity of symptom expression to cachexia disease of mandarins and tangelos caused by the hop stunt viroid (HSVd) related citrus viroid II (CVd-II), as well as the detection of CVd-II variants in CGB infected Washington navel and Dortyol sweet orange, a Turkish cultivar. A survey was made of 67 clones of CVd-II related variants recovered from severe CGB symptomatic and non-symptomatic trees of the same cultivars growing in close proximity. Only CVd-IIa, a non-cachexia inducing variant, was found in non-symptomatic Washington navel trees and no CVd-II variants were recovered from the Dortyol control. CGB infected sources contained a number of CVd-II related variants with the predominant species detected closely related to CVd-IIc, a known cachexia inducing viroid. Biological activity of representactive variants from CGB sources was determined by transmission to citron ( Citrus medica) as well as by bioassay on the indexing host for cachexia, Parson's Special mandarin (Citrus reticulata).