A method for the specific detection of the nucleolus organizing regions (NORs) of plant chromosomes has been developed employing enzymatic maceration and successive flame-drying for chromosome spreading and incubation with aqueous 50% AgNO3 at 55-60 C. When this method was applied to metaphase chromosomes the NORs were specifically discriminated as heavily stained segments in all the plant species examined. In the satisfactory results obtained by monitoring the reaction under a microscope during the course of the silver treatment, the chromosome arms were stained yellow to light brown while the NORs were dark brown to black. The present method has the advantage of yielding highly reproducible results for the specific detection of the NORs in plant materials.