Yield losses and reduced crop quality, caused by plant viruses are an increasing problem. Several important plant viruses are, in addition to their sap and vector transmission, also transmitted through seed. Seed transmission of plant pathogens plays an important role for the early outbreak of diseas in a crop, for the survival of inoculum from one crop season to the next, and for its international dispersal. Freedom from seedborne viral infection can be revealed by certain seed health testing methods. This book provides a practical guide to the commonly used detection methods for seed-transmitted viruses and viroids affecting both tropical and non-tropical crops.