This is an essential bench book that describes the molecular biology, structure, detection, purification, and pathogenesis of viroids and satellites. The volume begins with an overview of the current status of the field, followed by four chapters describing details of methodology, nucleic acid probes, purification, sequence variation, complementary RNA probes, polyacrylamide gel electrophoresis and mutational analysis of viroid movement and pathogenicity. Remaining chapters discuss such topics as viroids that cause apple scar disease in China, the cadang-cadang disease of palms in the Pacific area, viroid-like satellite RNAs, and a comparison of plant viroids with the human-pathogenic delta agent. The book will be a major reference work on viroids for years to come and an essential resource for virologists, molecular biologists, microbiologists, geneticists, biochemists, biomedical investigators, plant pathologists, and agricultural researchers.