The article briefly presents the design and chemical synthesis of parallel stranded DNA with formation of reverse Watson-Crick base pairs. Tchurikov et al attempted an analysis of parallel RNA-RNA duplex formation. Single stranded RNA, prepared by in vitro transcription with T7 polymerase using 33P and 3H nucleoside 5'-triphosphates, were appropriately hybridized and analysed by polyacrylamide gel electrophoresis prior and after RNAze A digestion. Results obtained allow to conclude on the formation of parallel stranded, RNaze A - stable RNA. The presented data show the importance of intramolecular parallel association of the single stranded RNA during its folding.