To eliminate infected budwood trees, various methods were used to detect citrus exocortis viroid (CEV). Screening over 1800 trees resulted in the detection of 4 groups of viroids as determined by RNA homology and length in nucleotides. CEV was the only member of the first group and was the largest viroid detected, with 371 bases. CEV almost invariably occurred with other viroids of lower molecular weight. To confirm any causal relationship between individual viroids and field symptoms, viroids representative of each group were purified and used to inoculate Etrog citron. Tissue from these citrons was used to inoculate young field trees with viroids, singly and in combination: assessment of the inoculations is continuing.