Both components of the virus complex that cause the sweetpotato virus disease (SPVD) in Nigeria can individually be transmitted by their respective vectors from diseased sweetpotato to healthy sweetpotato and to test plant, Ipomoea setosa. But in Isolation, neither the aphid nor the whitefly-transmitted component, both latent in sweetpotato, can be thus transmitted. The aphid-transmitted component does not reach concentrations in sweetpotato that are detectable by ELISA or ISEM, unless the plants are simultaneously infected with the whitefly-transmitted component, which has been isolated from this complex; however, its properties remain largely unknown. The aphid-transmitted component is serologically closely related to, or identical with, sweetpotato feathery mottle virus (FMV). The apparently, extremely low concentration in sweetpotato of the potyvirus (FMV) component of SPVD, as well as the hitherto unknown properties of the whitefly-transmitted disease component, has special implications for developing reliable indexing procedures for each of the viruses.  We have developed a simple testing procedure, based on the interdependence of both viruses, at IITA, it seems to provide a reliable indexing method for detecting both components of SPVD. SPVD, or very similar complex diseases have been identified from various other countries in Africa, and Taiwan.