Analysis of the sequence ITS1-5.8S-ITS2 in 11 samples of the amaranth species (Amaranthus caudatus, A. cruentus, A. hybridus, A. tricolor, A. paniculatus, A. hypohondriacus) was performed. It has been shown that the variability of the sequences of the intergenic spacers ITS1, ITS2 and 5.8S rRNA gene of the amaranth species analyzed is extremely low. A possible secondary structure of the 5.8S rRNA molecule was determined for the first time; three conservative motifs were identified. A single nucleotide substitution found in A. hybridus did not change the loop topology. In the sample of Celosia cristata taken as an external group, a four-nucleotide insertion in the 5′-end of the gene and a one-nucleotide deletion in the fourth hairpin not affecting the general topology of the 5.8S rRNA molecule were found. © 2014, Pleiades Publishing, Inc.