Root-knot nematodes (RKN) cause important production losses of rice (Oryza sativa L.) in the world. Together with Meloidogyne graminicola Golden and Birchfield 1965, M. oryzae Maas, Sanders and Dede, 1978 and M. salasi Lopez, 1984 have been causing damages in irrigated rice fields in Central and South America. In addition, six other RKN species may occur in rice fields in other regions of the world. Correct identification of Meloidogyne spp. is difficult but essential for the management of rice RKNs. The objective of this study was to develop some species-specific molecular markers for the diagnosis of South American RKN rice-related species. Isozyme phenotypes indicated the occurrence of some RKN species in the Brazilian samples, namely M. graminicola, M. oryzae, M. javanica, and two cryptic species designated as Meloidogyne sp. 2 and Meloidogyne sp. 3. Random amplified polymorphic DNA (RAPD) analysis of 16 isolates revealed interspecific genetic polymorphism between Meloidogyne spp., but isolates belonging to the same species (i.e., sharing the same esterase phenotype) always clustered together, whatever the species considered. Specific SCAR markers of 230, 120, and 160 bp were developed for M. graminicola, M. oryzae, and M. salasi, respectively. These SCAR markers may be potential molecular tools for application in routine diagnostic procedures subject to their validation with other rice RKN field populations in the world.