Isozymes and restriction fragment length polymorphisms (RFLPs) are convenient genetic markers for plant breeders and plant taxonomists. The application of these molecular markers to citrus genetics is discussed here. Isozymes have proven reliable tools for distinguishing nucellar from zygotic plants and monitoring in vitro, culture tissues. They are also helpful for assessing the citrus genetic organization: cultivar identification, heterozygosity, phylogeny. RFLP's have a similar scope of application, but can secure a greater resolving power. As a reason, they are used for exploring the entire genome, or for constructing detailed genetic mapping where the genes with desirable traits will be localized.