The first change observed in cells of leaves systemically infected with strawberry latent ringspot virus was the formation of inclusion bodies near the nucleus. The inclusions were largely composed of endoplasmic reticulum, complex membranous structures and ribosomes. Three days later their outer parts contained unbranched, double-walled, slightly flexuous tubules about 50 nm. wide and up to at least 2.5 um. long. Each tubule, or occasionally two or three tubules, was enclosed in a membranous sheath 80 to 120 nm. in diameter, joined to the endoplasmic reticulum. The tubules contained a single row of up to 100 or more darkly stained virus-like particles. Some tubules ended within the inclusion and some at plasmodesmata, in which virus-like particles occurred. The central, predominantly membranous, regions of the inclusions contained masses of faintly stained, apparently hollow structures resembling empty shells of virus coat protein.