Multiplex PCR assays were developed for the simultaneous detection of ten important Korean quarantine phytoplasmas. The species-specific primers were designed based on ribosomal protein, putative preprotein translocase Y, immunodominant protein, elongation factor TU, chaperonin protein and the 16S rRNA genes of ``Candidatus (Ca.) Phytoplasma`` species. Three main primer sets were prepared from ten designed primer pairs to limit nonspecific amplification as much as possible. The multiplex PCR assay using the three primer sets successfully amplified the correct conserved genes for each ``Ca. Phytoplasma`` species. In addition, ten important ``Ca. Phytoplasma`` species could be easily determined by recognizing band patterns specific for each phytoplasma species from three primer sets. Moreover, a high sensitivity of multiplex PCR for each primer set was observed for samples containing a low DNA concentration (10 ng/ul). This study provides the useful multiplex PCR assay as a convenient method to detect the presence of ten important quarantine phytoplasmas in Korea.