Heavy metals, such as cadmium, have a significant impacton plant physiology. However, their potential effect onplant–pathogen interaction, an important biological pro-cess, has not been examined. This study shows thatexposure of tobacco plants to non-toxic concentrations ofcadmium completely blocked viral disease caused by tur-nip vein clearing virus. Cadmium-mediated viral protectionwas due to inhibition of the systemic movement of thevirus, i.e. its spread from the inoculated into inoculated leaves. Exposure of plants to cadmium had no effect onviral replication, assembly and local movement within theinoculated leaf. Analysis of the viral presence in differenttissues suggested that cadmium treatment inhibited virusexit from the vascular tissue into uninoculated leavesrather than its entry into the host plant vasculature. Higher,toxic levels of cadmium did not produce this inhibitory effect on viral movement, allowing the systemic spreadof the virus and development of the viral disease. Theseobservations suggest that cadmium-induced viral protec-tion requires a relatively healthy, unpoisoned plant inwhich non-toxic levels of cadmium may trigger the produc-tion of cellular factors which interfere with the viral sys-temic movement.