Four new primers were designed, based on comparison of Physarum polycephalum sequences retrieved from Genbank (primers PHYS-5 and PHYS-4) and our own sequences (primers PHYS-3 and PHYS-2), to amplify the ITS regions of rDNA, including the 5.8S gene segment from Lamproderma species. Sequencing analysis shows that Lamproderma contains ITS1-5.8S-ITS2 regions of approximately 900 bp, which is similar in size to most eukaryotes. However, the corresponding region in another common myxomycete, Fuligo septica, is more than 2000 bp due to the presence of large direct-repeat motifs in ITS1. Myxomycete rDNA ITS regions are interesting both as phylogenetic markers in taxonomic studies and as model sequences for molecular evolution.