Cyclohexene nucleic acids (CeNA) with a D-like configuration form very stable self-complementary duplexes and stable duplexes with RNA. An increased duplex stability with Delta T(m)/mod of +1.2 degrees C is observed. The duplex with DNA is less stable. Excellent mismatch discrimination has been observed as well for the duplex with DNA as for the duplex with RNA. The results obtained with mixed CeNA sequences warrant antisense studies with CeNA. The CeNAs of opposite chirality constitute a self-pairing system on their own, resembling L-RNA sequences.